High 7.5Published Oct 15, 2026

CVE-2026-109855undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake

Updated under an hour ago (2026-10-19 10:00 UTC)

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It affects undici. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.28%, higher than 19% of scored CVEs.

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Every CVE for undici

Exploited in the last 30 days

undici is an HTTP client library for Node.js. In versions 8.11.0 and 8.11.1, its experimental WebSocket client, which is enabled by default when HTTP/2 is allowed, mishandles a failed WebSocket handshake over HTTP/2: the request is already marked completed, so the abort becomes a no-op and the underlying HTTP/2 stream is left open with no error listener. When a malicious server then destroys the connection, the orphaned stream emits an unhandled error and the Node.js process exits. A remote, unauthenticated server can therefore crash any client that opens a WebSocket to it over HTTP/2, resulting in a denial of service. The issue is fixed in undici 8.11.2, and users should upgrade to 8.11.2 or later. As a workaround, set allowH2 to false to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers.

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-248, CWE-754
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.28% (percentile 19)
Assigned by: openjs
NVD analysis: Awaiting Analysis
Record last updated: Oct 15, 2026
First seen by InfoSec Signals: Oct 15, 2026

Affected products

Affected products

undici undici undici:undici (from the name)	from 8.11.0 before 8.11.2; 8.11.2 not affected	CNA record

References

https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp
https://cna.openjsf.org/security-advisories.html

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.