Threat Intelligence Database

The asyncssh library has an incomplete fix for CVE-2026-45309, allowing a bypass of username sanitization in the AuthorizedKeysFile path. The fix in version 2.23.0 blocks usernames containing '/', '\', or '..' before substitution, but does not block leading '~' or environment variable expansions, which are later expanded and can escape the intended directory. This allows an attacker to redirect authorized-keys file lookup to another user's home directory by using a username like '~root'. The vulnerability impacts authentication by allowing pre-auth access to an attacker-controlled authorized-keys file if the server's AuthorizedKeysFile configuration starts with '%u'. A patch is available to address this issue.

AsyncSSH versions through 2.23.0 contain a path traversal vulnerability in the SCP client implementation. A malicious SSH server can send crafted filenames with directory traversal sequences to write arbitrary files outside the intended download directory. This allows overwriting critical user files such as ~/.bashrc, ~/.ssh/authorized_keys, and others, potentially leading to code execution. The vulnerability arises because filenames received from the server are not sanitized before being joined to the destination path. AsyncSSH 2.23.1 includes a fix for this issue.

A vulnerability in PyJWT's issuer (iss) claim validation allows partial string matches instead of exact matches. This occurs because the code mistakenly treats the issuer string as a sequence, causing substring checks rather than equality checks. The issue affects DVC versions from 3.56.0_2 up to but not including 3.58.0. Although the signature validation remains intact, this flaw could allow tokens with incorrect issuer claims to be accepted. The vulnerability has a low severity score and a patch is available.

AsyncSSH versions 2.14.1 and earlier are vulnerable to a prefix truncation attack (Terrapin attack) targeting the ChaCha20-Poly1305 and Encrypt-then-MAC SSH algorithms. This attack allows a man-in-the-middle to strip messages after the initial key exchange, breaking SSH extension negotiation and downgrading connection security. The vulnerability exploits the lack of authentication for SSH_MSG_IGNORE messages and sequence number checks only after key exchange. The attack is guaranteed to work on ChaCha20-Poly1305 and requires CBC ciphers for practical exploitation of Encrypt-then-MAC. A patch is available that implements a 'strict kex' handshake to prevent this attack, requiring support on both client and server sides. As a temporary mitigation, disabling affected algorithms and using alternatives like AES-GCM is recommended.