GHSA-38rv-x7px-6hhq
undici WebSocket client vulnerable to denial of service via cumulative fragment bypass
At a glance
- Published
- Updated
- CVE
- CVE-2026-9675
- CVSS_V3
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Description
## Impact 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.
Affected packages
| Package | Versions |
|---|---|
| npm · undici | introduced 8.0.0, fixed 8.5.0 |
References
- https://github.com/nodejs/undici/security/advisories/GHSA-38rv-x7px-6hhq WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-9675 ADVISORY
- https://cna.openjsf.org/security-advisories.html WEB
- https://github.com/nodejs/undici PACKAGE
Sources
| Source | Licence |
|---|---|
| OSV.dev | CC-BY 4.0 — GitHub Advisory Database |