{"id":"CVE-2026-109855","title":"undici is an HTTP client library for Node.js","summary":"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 alrea…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-248","CWE-754"],"vendor":"undici","product":"undici","affected":["undici >= 8.11.0 < 8.11.2"],"published":"2026-10-15","updated":"2026-10-15","sourceUpdated":"2026-10-15T09:17:16.573","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-109855","references":[{"url":"https://cna.openjsf.org/security-advisories.html","label":"ce714d77-add3-4f53-aff5-83d477b104bb"},{"url":"https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp","label":"ce714d77-add3-4f53-aff5-83d477b104bb"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-109855.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-109855"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2553103"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-109855"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-109855"}],"tags":["nvd","cve.org","csaf","vex","red-hat"],"ingestedAt":"2026-10-15T08:58:33.102Z","slug":"CVE-2026-109855","body":"## Overview\n\nundici 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Cryostat 4, Exploit Intelligence, Red Hat AMQ Broker 7, Red Hat Ansible Automation Platform 2, Red Hat Build of Podman Desktop, Red Hat Developer Hub, … · no fix planned: Secrets Management Console for Red Hat OpenShift, Cryostat 4, Exploit Intelligence, Red Hat AMQ Broker 7, … · updated 2026-10-15 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-109855.json)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}