VulnerabilityPublished 10 Nov 2026

CVE-2026-82391: zephyrproject zephyr · Memory-safety

Affects zephyrproject zephyrSource CVE Database V5

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Not known to be exploited · CVSS 9.1 Critical : upgrade to 4.5.0 or 4.3.2 as a priority.

Data as of 10 Nov 2026, 22:19 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (zephyr)	CVSS 3.1	9.1

Patch: Available – fixed in 4.5.0, 4.3.2

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade zephyrproject zephyr to 4.5.0 or 4.3.2.

Affected software

Product	Affected	Fixed in
zephyrprojectzephyr	Affected >=4.4.0 <4.5.0	Fixed in 4.5.0
zephyrprojectzephyr	Affected >=4.0.0 <4.3.2	Fixed in 4.3.2
GitHubzephyr`pkg:github/zephyr`Other threats	Affected >=4.0.0 <4.3.2 >=4.4.0 <4.5.0	Fixed in 4.3.2 4.5.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

The HTTP/2 front-end of the Zephyr HTTP server aliased connection receive state as a scratch output. In subsys/net/lib/http/http_server_http2.c, handle_http2_static_fs_resource() passed &client->data_len as the file_size out-parameter of http_server_find_file(). client->data_len is the count of unprocessed bytes remaining in the fixed-size per-connection receive buffer client->buffer[CONFIG_HTTP_SERVER_CLIENT_BUFFER_SIZE] (256 bytes by default), an invariant every frame handler and the socket receive path rely on. Serving any static file therefore replaced that bounded value with the file's on-disk size, and nothing resets it afterwards. The defect is reached by an unauthenticated HTTP/2 GET for any file under the web root, in applications that register a static-filesystem resource (HTTP_RESOURCE_TYPE_STATIC_FS) with CONFIG_FILE_SYSTEM=y; CONFIG_HTTP_SERVER_VERSION_2 is enabled by default and no TLS or credentials are required on this path. Once client->data_len exceeds the buffer size, the frame dispatch loop in subsys/net/lib/http/http_server_core.c keeps parsing past the end of the received data, and the peer controls the bytes at client->cursor, so it can choose which fabricated frame the state machine consumes next by appending bytes after its request. The inflated length defeats the only guards on the buffer. parse_http_frame_header() and the per-frame handlers read and skip up to a 24-bit frame length beyond the buffer (out-of-bounds read); the compaction memmove(client->buffer, client->cursor, client->data_len) at the end of request handling copies the file-size number of bytes into the 256-byte buffer, overflowing the rest of struct http_client_ctx — including the current_detail/current_stream pointers, the parser_settings function-pointer table and the inactivity_timer work handler — and the adjacent client contexts in static memory; and the subsequent zsock_recv(client->fd, client->buffer + client->data_len, sizeof(client->buffer) - client->data_len, 0) underflows its size argument, writing attacker-supplied data of attacker-chosen length out of bounds. The impact is remote memory corruption in the server's single address space: at minimum a crash or hang of the device, and plausibly control-data overwrite leading to code execution. The HTTP/1 and HTTP/3 static-filesystem handlers already used a local variable and are unaffected; the fix makes the HTTP/2 handler use a local size_t file_size as well.

References

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