Threat database

Time-of-check Time-of-use (TOCTOU) race condition vulnerability in Erlang/OTP ssl (dtls_packet_demux module) allows an unauthenticated remote attacker to crash all active DTLS sessions on a listener. A DTLS server listener uses a single shared dtls_packet_demux gen_server process to route incoming UDP datagrams to the correct connection handler. When a DTLS client reconnects rapidly from the same source address and port (sending multiple ClientHello messages in quick succession), a race condition in the demux's internal gb_trees key-value store causes a {key_exists, {old, Client}} crash, terminating the demux process. Because the demux is shared across all DTLS associations on that listener, its crash immediately kills every active DTLS session, not just the attacker's. The attack is pre-authentication: the attacker only needs to send UDP datagrams containing valid ClientHello messages from the same source IP and port before the intermediate DOWN monitor message is processed by the gen_server. No credentials, no completed handshake, and no special configuration are required, and the crash can be repeated indefinitely to create a persistent denial of service for all clients of that listener. This vulnerability is associated with program file lib/ssl/src/dtls_packet_demux.erl. This issue affects OTP from OTP 25.3 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 10.9 before 11.7.3, 11.6.0.3 and 11.2.12.10.

Use of Default Cryptographic Key vulnerability in Erlang/OTP ssl (DTLS server) allows predictable DTLS cookie computation during the startup window, enabling source address verification bypass. On DTLS server startup, dtls_server_connection:initial_hello/3 initializes previous_cookie_secret to the empty binary (<<>>) instead of a random value. Because HMAC with an empty key is deterministic, anyone who observes the plaintext ClientHello can compute dtls_handshake:cookie(<<>>, IP, Port, Hello) and forge a valid DTLS cookie before the first rotation of the cookie secret. The DTLS cookie (RFC 6347 §4.2.1) is a denial-of-service mitigation that prevents spoofed source IPs from forcing the server to allocate state and perform expensive cryptographic operations; it is not an authentication mechanism. During the window from server startup until the first secret rotation (0 to 15 seconds), an attacker who can observe the plaintext ClientHello can bypass the source address verification, enabling DTLS handshake amplification with spoofed source addresses. This vulnerability is associated with program file lib/ssl/src/dtls_server_connection.erl and program routine dtls_server_connection:initial_hello/3. This issue affects OTP from OTP 20.0 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 8.2 before 11.7.3, 11.6.0.3 and 11.2.12.10.

Improper Enforcement of Message Integrity During Transmission in a Communication Channel vulnerability in Erlang/OTP ssl (tls_gen_connection module) allows a network-positioned attacker to inject unauthenticated plaintext that the TLS client application later treats as authenticated server data. The function tls_gen_connection:handle_protocol_record/3 rejects APPLICATION_DATA records that arrive in pre-handshake states when the TLS endpoint acts as a server, but does not apply the same check when the endpoint acts as a client. A network-positioned attacker can send plaintext APPLICATION_DATA records to the client during the handshake. The records are buffered and, once the handshake completes successfully, delivered to the application as if they were authenticated post-handshake data. The attacker cannot observe the client's response or steer the connection, so the impact is limited to blind injection of unauthenticated bytes. The injection window is wider for TLS versions prior to TLS 1.3 than for TLS 1.3. This vulnerability is associated with program file lib/ssl/src/tls_gen_connection.erl. TLS 1.3 is affected starting with OTP 22.0, when TLS 1.3 support was added. This issue affects OTP from OTP 17.0 before OTP 27.3.4.14, from OTP 28.0 before OTP 28.5.0.3, and from OTP 29.0 before OTP 29.0.3, corresponding to ssl from 5.3.4 before 11.2.12.10, from 11.3 before 11.6.0.3, and from 11.7 before 11.7.3. Whether OTP before OTP 17.0, corresponding to ssl before 5.3.4, is affected is unknown.

Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in Erlang OTP ssh (ssh_sftpd module) allows an authenticated SFTP user to render an SFTP channel permanently unresponsive. The handle_data/4 function in ssh_sftpd contains a catch-all clause that accepts channel data of any type. When channel data with a non-zero type code (SSH_MSG_CHANNEL_EXTENDED_DATA) arrives with an empty pending buffer and a payload at or below the SFTP packet size limit, the clause tail-calls itself with identical arguments, creating an infinite loop. The SFTP protocol operates exclusively on normal channel data (type 0). Extended data (non-zero type) is meaningless for SFTP and is never sent by conforming clients. However, the SSH protocol permits any channel participant to send extended data on an open channel, so an authenticated SFTP client can trigger the loop by sending SSH_MSG_CHANNEL_EXTENDED_DATA with any data_type_code and any non-empty payload at or below the size limit. The targeted ssh_sftpd process enters an infinite tail-recursive loop. It never processes another message, its message queue grows without bound, and it can only be stopped by killing the process. BEAM's reduction-based scheduler preemption continues to function, so other processes on the node are not starved, but each stuck channel process consumes its full CPU time share continuously and accumulates unbounded message queue memory. Opening many channels amplifies the CPU and memory impact. Erlang/OTP SSH configurations using the default max_channels setting (infinity) allow an authenticated user to open unlimited channels per connection, amplifying the attack without requiring multiple TCP connections or authentications. No file contents, credentials, or write access are obtainable through this issue. The impact is limited to denial of service on targeted SFTP channels, with secondary CPU degradation and memory growth. This vulnerability is associated with program file lib/ssh/src/ssh_sftpd.erl and program routine ssh_sftpd:handle_data/4. This issue affects OTP from OTP 17.0 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssh from 3.0.1 before 6.0.2, 5.5.2.2 and 5.2.11.9.

The Erlang/OTP ssl application does not validate that the PSK identity list and binder list carried in a TLS 1.3 ClientHello pre-shared key extension have equal length before passing them to the session ticket handler. In tls_handshake_1_3:handle_pre_shared_key/3, an OfferedPreSharedKeys record with a mismatched number of identities and binders is forwarded directly to tls_server_session_ticket:use/4, which crashes the session ticket handler process. An unauthenticated remote attacker can send a single crafted ClientHello to a TLS 1.3 server with session tickets enabled (stateful or stateless mode) and permanently disrupt session ticket handling on that listener. New TLS 1.3 handshakes complete but subsequently crash when the server attempts to issue a session ticket, effectively making TLS 1.3 unusable on the affected listener until the ssl application is restarted. TLS 1.2 connections are not affected. This issue affects OTP from OTP 22.2 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 9.5 before 11.7.3, 11.6.0.3 and 11.2.12.10.

Observable Response Discrepancy vulnerability in Erlang OTP ssh (ssh_sftpd module) allows an authenticated SFTP user to enumerate the existence of files and directories outside the configured root directory. The SSH_FXP_REALPATH handler in ssh_sftpd calls relate_file_name/3 with Canonicalize=false, unlike every other SFTP operation handler. This allows .. components in the requested path to bypass the is_within_root/2 check without being resolved. The un-canonicalized path then enters resolve_symlinks/2, which walks up the directory tree above the configured root and issues read_link() syscalls on arbitrary filesystem paths. An authenticated SFTP client can exploit this by sending a REALPATH request with a crafted traversal path. The server response differs depending on whether the target path exists on the host filesystem (SSH_FXP_NAME when the path resolves successfully, SSH_FX_NO_SUCH_FILE when it does not). This creates a path-existence oracle that an attacker can use to enumerate the filesystem structure outside the configured root, including the existence of sensitive files, directories, and mount points. The vulnerability leaks only the existence of paths. No file contents, credentials, or write access are obtainable through this issue alone. The information gained may assist further attacks when combined with other vulnerabilities. This vulnerability is associated with program files lib/ssh/src/ssh_sftpd.erl and program routine ssh_sftpd:handle_op/4. This issue affects OTP from OTP 17.0 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssh from 3.0.1 before 6.0.2, 5.5.2.2 and 5.2.11.9.

Sensitive Data Exposure vulnerability in Erlang OTP inets (httpc_response module) allows Retrieve Embedded Sensitive Data. The httpc client forwards the Authorization and Proxy-Authorization request headers to redirect targets without checking whether the redirect crosses an origin boundary. httpc_response:redirect/2 constructs the redirected request by updating only the host field of the header record; all other fields (including authorization and proxy_authorization) are copied verbatim. The redirect target host is never compared against the original host. autoredirect defaults to true, so this affects all httpc callers that do not explicitly disable automatic redirects. An attacker who controls a server that the victim contacts via httpc can issue a cross-origin 3xx redirect to a server they also control. The Authorization header (including Basic credentials derived from URL userinfo via httpc_request:handle_user_info/2) is forwarded to the redirect target, allowing credential theft. The same applies to the Proxy-Authorization header. This vulnerability is associated with program files lib/inets/src/http_client/httpc_response.erl. This issue affects OTP from OTP 17.0 before OTP 27.3.4.19, OTP 28.5.0.8, and OTP 29.1.2, corresponding to inets from 5.10 before 9.3.2.8, 9.6.2.4, and 9.8.1. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Reliance on IP Address for Authentication vulnerability in Erlang/OTP ssl (inet_tls_dist module) allows unauthenticated bypass of the distribution-over-TLS LAN allowlist. The inet_tls_dist:check_ip/1 function, which enforces a LAN allowlist for Erlang distribution over TLS, calls inet:sockname/1 instead of inet:peername/1 to obtain the peer's IP address. Because inet:sockname/1 returns the local socket address, both the local IP and the supposed peer IP resolve to the same value, causing the subnet mask comparison to always succeed regardless of the actual remote address. Any holder of a CA-signed TLS certificate can therefore bypass the LAN restriction and gain full Erlang distribution access to the node, including rpc:call/4 and code:load_binary/3. This vulnerability is associated with program file lib/ssl/src/inet_tls_dist.erl. This issue affects OTP from OTP 26.0 before OTP 27.3.4.13, OTP 28.5.0.2, and OTP 29.0.2, corresponding to ssl from 11.0 before 11.2.12.9, 11.6.0.2, and 11.7.2.

Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Erlang OTP ssh (ssh_sftpd module) allows File Discovery. The SSH_FXP_READLINK handler in ssh_sftpd sends the raw result of file:read_link/2 to the client without calling chroot_filename/2 to strip the backend root prefix. An authenticated SFTP client can create a symlink inside the chroot pointing to /; ssh_sftpd resolves the target to the absolute backend root and stores it on disk. Reading the symlink back via SSH_FXP_READLINK returns that absolute path, for example /data/sftp, instead of the chrooted value /. The information disclosed is the absolute filesystem path of the SFTP root directory and of any symlink targets within it. No file contents, credentials, or access to paths outside the root directory are obtainable through this issue alone. This vulnerability is associated with program files lib/ssh/src/ssh_sftpd.erl. This issue affects OTP from OTP 17.0 before OTP 27.3.4.13, OTP 28.5.0.2, and OTP 29.0.2, corresponding to ssh from 3.0.1 before 5.2.11.8, 5.5.2.1, and 6.0.1. Whether OTP before OTP 17.0, corresponding to ssh before 3.0.1, is affected is unknown.

Server-Side Request Forgery (SSRF) vulnerability in Erlang/OTP ftp (ftp_internal module) allows FTP bounce attacks and SSRF via an unvalidated PASV response IP address. The ftp_internal:handle_ctrl_result/2 PASV handler (mode=passive, ipfamily=inet, ftp_extension=false) extracts the IP address from the server's 227 response and passes it directly to gen_tcp:connect/4 without validating it against the control connection peer address. The adjacent EPSV handlers correctly call peername(CSock) to derive the IP from the control connection, but the PASV handler does not. A malicious or compromised FTP server can redirect the client's data connection to an arbitrary internal host and port. On read operations (ftp:ls/1,2, ftp:nlist/1,2, ftp:recv/2,3), data from the redirected target is returned to the caller. On write operations (ftp:send/2,3, ftp:append/2,3), file content is sent to the redirected target. This enables SSRF against internal hosts, cloud metadata endpoints, and FTP bounce attacks against third-party hosts. The vulnerable path is the default configuration (mode=passive, ipfamily=inet, ftp_extension=false). RFC 2577 section 3 explicitly recommends validating the PASV response IP against the control connection peer. The ftp application is deprecated and scheduled for removal in OTP-30. This vulnerability is associated with program files lib/inets/src/ftp/ftp_internal.erl (inets 5.10.4 through 6.5, OTP 17.4 through 20.3) and lib/ftp/src/ftp_internal.erl (ftp 1.0 and later, OTP 21.0 and later). This issue affects OTP from OTP 17.4 before OTP 29.0.2, OTP 28.5.0.2 and OTP 27.3.4.13, corresponding to inets from 5.10.4 before 7.0 and ftp from 1.0 before 1.2.6, 1.2.4.1 and 1.2.3.1.

Observable Timing Discrepancy vulnerability in Erlang/OTP ssh (ssh_auth, ssh_options modules) allows unauthenticated remote username enumeration via timing side-channel in password authentication. When the SSH daemon is configured with the user_passwords or password option, ssh_auth:check_password/3 performs a PBKDF2-SHA256 computation with 600,000 iterations (~300ms) for valid usernames, but returns immediately (~0ms) for invalid usernames via the ssh_options:get_password_option/2 path. This timing difference is detectable in a single authentication attempt and allows an unauthenticated attacker to distinguish valid from invalid usernames. The user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability. This vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl. This issue affects OTP from OTP 29.0 before OTP 29.0.2, corresponding to ssh from 6.0 before 6.0.1.

Stack-based Buffer Overflow vulnerability in Erlang OTP erts (inet_drv) allows an unauthenticated remote attacker to crash the BEAM VM by sending a crafted SCTP ERROR chunk. The sctp_parse_error_chunk function in erts/emulator/drivers/common/inet_drv.c parses SCTP ERROR chunks and writes cause codes into a fixed-size stack-allocated ErlDrvTermData spec[] array without checking bounds. A remote attacker who has established an SCTP association to a listening port can send a single crafted SCTP ERROR chunk containing enough cause codes to overflow the stack buffer, crashing the VM. The attacker can only write 16-bit values interleaved with a fixed tag, so the overflow does not provide a controlled return address, limiting exploitation to Denial of Service. A crafted SCTP ERROR chunk may also leak bits and pieces of Erlang VM memory into the received error packet observed by the Erlang process. Such data is already readable by the user running the Erlang VM, so the disclosure scope is limited. This issue affects OTP from OTP 17.0 before OTP 27.3.4.13, OTP 28.5.0.2, and OTP 29.0.2, corresponding to erts from 6.0 before 15.2.7.9, 16.4.0.2, and 17.0.2. Whether OTP before OTP 17.0, corresponding to erts before 6.0, is affected is unknown.

Stack-based Buffer Overflow vulnerability in Erlang OTP (erl_interface) allows Stack-based Buffer Overflow. This vulnerability is associated with program file lib/erl_interface/src/misc/ei_printterm.c and program routine ei_s_print_term. The C function ei_s_print_term uses an internal 2000-character stack buffer to format terms. When called with an encoded Erlang term containing a very large integer (encoded representation exceeding 2000 characters), the buffer overflows. The overflow bytes are restricted to the ASCII values of 0-9 and A-F, which limits exploitation to Denial of Service. The companion function ei_print_term, which prints directly to a FILE instead of a memory buffer, does not contain this bug. This issue affects OTP from OTP 17.0 before OTP 27.3.4.13, OTP 28.5.0.2, and OTP 29.0.2, corresponding to erl_interface from 3.7.16 before 5.5.2.1, 5.7.0.1, and 5.8.1. Whether OTP before OTP 17.0, corresponding to erl_interface before 3.7.16, is affected is unknown.

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_cert and public_key modules) allows a DNS nameConstraints bypass via subject CommonName fallback in TLS hostname verification. Two flaws combine to allow a subordinate CA whose DNS nameConstraints are restricted (e.g. permitted;DNS:allowed.example.com) to issue a leaf certificate that an OTP TLS client accepts as a valid identity for an out-of-scope hostname (e.g. victim.example.com): First, pubkey_cert:validate_names/6 in lib/public_key/src/pubkey_cert.erl only checks SAN DNS entries against nameConstraints. Per RFC 5280, a permitted DNS subtree only restricts certificates that contain a DNS-typed name. A leaf with no subjectAltName therefore trivially satisfies any permitted;DNS:... constraint regardless of its subject commonName. Second, public_key:pkix_verify_hostname/3 in lib/public_key/src/public_key.erl falls back to the subject commonName when no subjectAltName is present, extracting id-at-commonName attributes as presented IDs and matching them against the reference hostname. The strict pkix_verify_hostname_match_fun(https) matcher does not suppress this fallback. The result is that path validation accepts a CN-only leaf under a DNS-constrained intermediate (no SAN means the nameConstraints are not triggered), and hostname verification then accepts it via the CN fallback. The bypass is reachable from stock ssl:connect with verify_peer, a trusted CA, SNI, and the canonical strict https hostname matcher. This issue affects OTP from OTP 19.3 before OTP 29.0.1, OTP 28.5.0.1, OTP 27.3.4.12 and OTP 26.2.5.21, corresponding to public_key from 1.4 before 1.21.1, 1.20.3.1, 1.17.1.3 and 1.15.1.7.

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_ocsp module) allows forged OCSP responses signed with an expired responder certificate to be accepted as valid. OCSP response verification in pubkey_ocsp:verify_response/5 and pubkey_ocsp:is_authorized_responder/3 in lib/public_key/src/pubkey_ocsp.erl does not check the validity period (notBefore/notAfter) of the OCSP responder certificate. An attacker who has obtained the private key of an expired CA-designated OCSP responder certificate can forge OCSP responses that Erlang/OTP accepts as valid. This affects TLS clients using OCSP stapling via the ssl application: a malicious or compromised server can present a revoked TLS certificate together with a forged OCSP response signed by an expired responder key, and the client will accept the revoked certificate as valid. It also affects applications calling public_key:pkix_ocsp_validate/5 directly, where the impact depends on the use case — server-side client certificate validation using this API may allow authentication bypass with a revoked client certificate. This issue affects OTP from OTP 27.0 before OTP 29.0.1, OTP 28.5.0.1 and OTP 27.3.4.12, corresponding to public_key from 1.16 before 1.21.1, 1.20.3.1 and 1.17.1.3.

Improper Following of a Certificate's Chain of Trust vulnerability in Erlang OTP public_key (pubkey_cert module) allows a non-CA certificate to be accepted as an intermediate issuer, enabling certificate chain forgery. In lib/public_key/src/pubkey_cert.erl, pubkey_cert:validate_extensions/7 contains two flaws that together allow a certificate with basicConstraints cA:false and no keyUsage extension to be used as an intermediate issuer in a chain passed to public_key:pkix_path_validation/3: the cA:false clause recurses into the remaining extensions without rejecting the certificate when it is in issuer position, and the keyUsage check only fires when the extension is present, so a certificate lacking keyUsage entirely bypasses the keyCertSign enforcement. Any party holding an end-entity certificate with basicConstraints cA:false and no keyUsage extension, issued by any CA in the victim's trust store, can use that certificate's private key to sign forged leaf certificates for arbitrary identities. public_key:pkix_path_validation/3 accepts the resulting chain, and by extension every TLS or mTLS endpoint built on the OTP ssl application that relies on the default verifier is affected, including server identity verification on the client side and client certificate verification on mTLS servers. This issue affects OTP from OTP 17.0 before OTP 27.3.4.19, OTP 28.5.0.8, and OTP 29.1.2, corresponding to public_key from 0.22 before 1.17.1.7, 1.20.3.6, and 1.21.8. Whether OTP before OTP 17.0, corresponding to public_key before 0.22, is affected is unknown.

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') vulnerability in Erlang OTP ssh (ssh_sftpd module) allows an authenticated SFTP user to modify file attributes outside the configured chroot directory. The SFTP daemon (ssh_sftpd) stores the raw, user-supplied path in file handles instead of the chroot-resolved path. When SSH_FXP_FSETSTAT is issued on such a handle, file attributes (permissions, ownership, timestamps) are modified on the real filesystem path, bypassing the root directory boundary entirely. Any authenticated SFTP user on a server configured with the root option can modify file attributes of files outside the intended chroot boundary. The prerequisite is that a target file must exist on the real filesystem at the same relative path. Note that this vulnerability only allows modification of file attributes; file contents cannot be read or altered through this attack vector. If the SSH daemon runs as root, this enables direct privilege escalation: an attacker can set the setuid bit on any binary, change ownership of sensitive files, or make system configuration world-writable. This vulnerability is associated with program files lib/ssh/src/ssh_sftpd.erl and program routines ssh_sftpd:do_open/4 and ssh_sftpd:handle_op/4. This issue affects OTP from OTP 17.0 before OTP 28.4.3, OTP 27.3.4.11 and OTP 26.2.5.20, corresponding to ssh from 3.0.1 before 5.5.3, 5.2.11.7 and 5.1.4.15.

Incorrect Authorization vulnerability in Erlang OTP (inets modules) allows unauthenticated access to CGI scripts protected by directory rules when served via script_alias. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory-based access controls against the DocumentRoot-relative path while mod_cgi executes the script at the ScriptAlias-resolved path. This path mismatch allows unauthenticated access to CGI scripts that directory rules were meant to protect. This vulnerability is associated with program files lib/inets/src/http_server/mod_alias.erl, lib/inets/src/http_server/mod_auth.erl, and lib/inets/src/http_server/mod_cgi.erl. This issue affects OTP from OTP 17.0 before OTP 26.2.5.19, OTP 27.3.4.10, and OTP 28.4.2, corresponding to inets from 5.10 before 9.1.0.6, 9.3.2.4, and 9.6.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.

Improper Certificate Validation vulnerability in Erlang OTP public_key (pubkey_ocsp module) allows OCSP designated-responder authorization bypass via missing signature verification. The OCSP response validation in public_key:pkix_ocsp_validate/5 does not verify that a CA-designated responder certificate was cryptographically signed by the issuing CA. Instead, it only checks that the responder certificate's issuer name matches the CA's subject name and that the certificate has the OCSPSigning extended key usage. An attacker who can intercept or control OCSP responses can create a self-signed certificate with a matching issuer name and the OCSPSigning EKU, and use it to forge OCSP responses that mark revoked certificates as valid. This affects SSL/TLS clients using OCSP stapling, which may accept connections to servers with revoked certificates, potentially transmitting sensitive data to compromised servers. Applications using the public_key:pkix_ocsp_validate/5 API directly are also affected, with impact depending on usage context. This vulnerability is associated with program files lib/public_key/src/pubkey_ocsp.erl and program routines pubkey_ocsp:is_authorized_responder/3. This issue affects OTP from OTP 27.0 before OTP 28.4.2 and OTP 27.3.4.10, corresponding to public_key from 1.16 before 1.20.3 and 1.17.1.2, and ssl from 11.2 before 11.5.4 and 11.2.12.7.