--- id: CVE-2026-19534 title: >- undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested summary: >- undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested. A default WebSocket connection sends no subprotocol, but if the server's … 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-252 - CWE-476 vendor: nodejs product: undici affected: - 'undici >= 6.7.0, < 6.28.1' - 'undici >= 7.0.0, < 7.29.1' - 'undici >= 8.0.0, < 8.10.2' patched: - undici 8.10.2 published: '2026-09-04' updated: '2026-09-16' sourceUpdated: '2026-09-16T20:41:08.750' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19534' references: - url: 'https://cna.openjsf.org/security-advisories.html' label: ce714d77-add3-4f53-aff5-83d477b104bb - url: 'https://github.com/nodejs/undici/security/advisories/GHSA-rfgv-xxqx-mfg5' label: ce714d77-add3-4f53-aff5-83d477b104bb - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-19534.json - url: 'https://access.redhat.com/security/cve/CVE-2026-19534' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2528759' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-19534' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-19534' - url: 'https://access.redhat.com/errata/RHSA-2026:66008' - url: 'https://access.redhat.com/errata/RHSA-2026:66605' - url: 'https://access.redhat.com/errata/RHSA-2026:69248' - url: 'https://access.redhat.com/errata/RHSA-2026:72712' - url: 'https://access.redhat.com/errata/RHSA-2026:72722' - url: >- https://github.com/nodejs/undici/commit/2af0faf88b906d3127a360c3ac75164c0f95e5a5 - url: >- https://github.com/nodejs/undici/commit/6615e0175e9b635bcd2e3e87a47daa82f6f5b728 - url: >- https://github.com/nodejs/undici/commit/66e12816064cf3068f63bd134748b7fc4e779bad - url: 'https://github.com/nodejs/undici/releases/tag/v6.28.1' - url: 'https://github.com/nodejs/undici/releases/tag/v7.29.1' - url: 'https://github.com/nodejs/undici/releases/tag/v8.10.2' - url: 'https://github.com/advisories/GHSA-rfgv-xxqx-mfg5' - url: 'https://access.redhat.com/errata/RHSA-2026:73428' - url: 'https://access.redhat.com/errata/RHSA-2026:71017' - url: 'https://access.redhat.com/errata/RHSA-2026:74085' - url: 'https://access.redhat.com/errata/RHSA-2026:73838' - url: 'https://access.redhat.com/errata/RHSA-2026:74609' - url: 'https://access.redhat.com/errata/RHSA-2026:75864' - url: 'https://access.redhat.com/errata/RHSA-2026:75870' - url: 'https://access.redhat.com/errata/RHSA-2026:76750' - url: 'https://access.redhat.com/errata/RHSA-2026:82151' - url: 'https://access.redhat.com/errata/RHSA-2026:76788' - url: 'https://access.redhat.com/errata/RHSA-2026:79088' - url: 'https://access.redhat.com/errata/RHSA-2026:84703' - url: 'https://access.redhat.com/errata/RHSA-2026:84589' - url: 'https://access.redhat.com/errata/RHSA-2026:84734' tags: - nvd - csaf - vex - red-hat - ghsa - npm epss: 0.00394 epssPercentile: 0.33411 ingestedAt: '2026-09-08T19:08:49.593Z' aliases: - GHSA-rfgv-xxqx-mfg5 ecosystem: npm --- ## Overview undici's WebSocket client crashes the whole Node.js process during the opening handshake when a server responds with a subprotocol that the client never requested. A default WebSocket connection sends no subprotocol, but if the server's 101 response includes a Sec-WebSocket-Protocol header, undici dereferences a null value while checking it against the requested list and throws an uncaught TypeError. Because that code runs inside a microtask with no surrounding error handling, the exception propagates and terminates the process under Node's default behavior, instead of gracefully failing the connection as required by the WebSocket protocol. Any application that opens a WebSocket to an attacker-controlled or compromised server, or over a plaintext connection subject to a machine-in-the-middle, can be crashed remotely without authentication in the default configuration. This affects undici versions from 6.7.0 up to 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2. ## Affected - `undici >= 6.7.0, < 6.28.1` - `undici >= 7.0.0, < 7.29.1` - `undici >= 8.0.0, < 8.10.2` ## Remediation Upgrade past the affected range: - `undici 8.10.2` ## Vendor advisories - **Red Hat VEX** · Important · affected: Exploit Intelligence, OpenShift Pipelines, Red Hat Build of Podman Desktop, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · no fix planned: Red Hat Hardened Images, Secrets Management Console for Red Hat OpenShift, Exploit Intelligence, OpenShift Pipelines, … · updated 2026-10-19 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-19534.json) - **RHSA-2026:66008** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-09 · [advisory](https://access.redhat.com/errata/RHSA-2026:66008) - **RHSA-2026:66605** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-11 · [advisory](https://access.redhat.com/errata/RHSA-2026:66605) - **RHSA-2026:69248** · Red Hat · fixed in: Red Hat Developer Hub 1.9 · released 2026-09-21 · [advisory](https://access.redhat.com/errata/RHSA-2026:69248) - **RHSA-2026:72712** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.1 · released 2026-09-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:72712) - **RHSA-2026:72722** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.2 · released 2026-09-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:72722) - **RHSA-2026:73428** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10) · released 2026-09-29 · [advisory](https://access.redhat.com/errata/RHSA-2026:73428) - **RHSA-2026:71017** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:71017) - **RHSA-2026:74085** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8) · released 2026-09-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:74085) - **RHSA-2026:73838** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9) · released 2026-09-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:73838) - **RHSA-2026:74609** · Red Hat · fixed in: Cluster Observability Operator 1.5.3 · released 2026-10-01 · [advisory](https://access.redhat.com/errata/RHSA-2026:74609) - **RHSA-2026:75864** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10) · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:75864) - **RHSA-2026:75870** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 8) · released 2026-10-05 · [advisory](https://access.redhat.com/errata/RHSA-2026:75870) - **RHSA-2026:76750** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9) · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:76750) - **RHSA-2026:82151** · Red Hat · fixed in: Red Hat Ansible Automation Platform 2.2 · released 2026-10-13 · [advisory](https://access.redhat.com/errata/RHSA-2026:82151) - **RHSA-2026:76788** · Red Hat · fixed in: Red Hat Developer Hub 1.10 · released 2026-10-06 · [advisory](https://access.redhat.com/errata/RHSA-2026:76788) - **RHSA-2026:84703** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v. 10.0) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84703) - **RHSA-2026:84589** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream EUS (v.9.6) · released 2026-10-19 · [advisory](https://access.redhat.com/errata/RHSA-2026:84589) ## Package advisory (CVE-2026-19534) Affected packages: - `undici >= 6.7.0, < 6.28.1` - `undici >= 7.0.0, < 7.29.1` - `undici >= 8.0.0, < 8.10.2` Patched in: - `undici 6.28.1` - `undici 7.29.1` - `undici 8.10.2` Source: https://github.com/advisories/GHSA-rfgv-xxqx-mfg5