CVE-2026-9675

NameCVE-2026-9675
DescriptionImpact: The undici WebSocket client enforces maxPayloadSize per-frame but does not enforce the cumulative size of fragmented uncompressed messages. A malicious WebSocket server can stream many small fragments that each pass per-frame validation but collectively exceed the configured limit, causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service. Affected applications are those using the undici WebSocket client (new WebSocket(...)) that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. This is a regression specific to undici 8.1.0. The 6.25.0 line shipped the equivalent cumulative check from the start and is unaffected. The 7.x line never had the maxPayloadSize feature and is also unaffected. Patches: Upgrade to undici >= 8.5.0. Workarounds: No workaround is available. The fix must be applied through an upgrade.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
node-undici (PTS)bookworm5.15.0+dfsg1+~cs20.10.9.3-1+deb12u4fixed
bookworm (security)5.15.0+dfsg1+~cs20.10.9.3-1+deb12u3fixed
trixie7.3.0+dfsg1+~cs24.12.11-1fixed
forky, sid7.24.6+dfsg+~cs3.2.0-3fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
node-undicisource(unstable)(not affected)

Notes

- node-undici <not-affected> (Vulnerable code not present)
https://github.com/nodejs/undici/security/advisories/GHSA-38rv-x7px-6hhq

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