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CRITICAL

CVE-2026-5067

CVE-2026-5067 — Out-of-bounds read/write in HTTP WebSocket upgrade via non-null-terminated Sec-WebSocket-Key

A remote, unauthenticated attacker can trigger memory corruption in Zephyr's HTTP server WebSocket upgrade path by sending a crafted Sec-WebSocket-Key header. The HTTP/1 header parser copies the header into a fixed-size buffer using a bounded copy that does not guarantee NUL termination when the input length reaches the buffer size. During upgrade handling the buffer is copied to a local stack buffer and passed to strlen(); if no NUL exists in-bounds, strlen() reads beyond the stack buffer and subsequent concatenation with the WebSocket magic string can write out of bounds. This leads to out-of-bounds read and write on stack memory, resulting in crash (denial of service) and potentially code execution. The path is reachable when CONFIG_HTTP_SERVER_WEBSOCKET is enabled.

Published Updated Sources: cvelistV5, zephyr

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

1%

chance of exploitation in 30 days

Affects

zephyrproject rtos

zephyr

CVSS base

9.8

CRITICAL

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

PoC

none · proof-of-concept · active

Automatable

Yes

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Affected scope

The catalog records vendors and products as separate lists, not pairs, so which product belongs to which vendor is not something this page can say.

Products (1)

zephyr

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactSource
9.8CVSS 3.1CRITICAL——cvelistV5

Weakness & attack patterns

  • CWE-170
  • CWE-787

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

  • Search application, proxy, and WAF logs for requests touching /1.

References

1 on the record

Elsewhere on this site

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.