EUVD-2026-71636Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Network-reachable crash with no authentication or user interaction required; impact is availability-only (deterministic process termination), with no confidentiality or integrity loss.
Primary rating from Vendor (openjs).
CVSS VectorVendor: openjs
Lifecycle Timeline
3DescriptionCVE.org
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.
Articles & Coverage 1
AnalysisAI
Process-terminating denial of service in undici's WebSocket implementation allows remote unauthenticated attackers to crash any Node.js application that connects to an attacker-controlled or machine-in-the-middle-intercepted WebSocket endpoint. During the opening handshake, if a server returns a Sec-WebSocket-Protocol header that the client never offered, undici dereferences a null value and throws an uncaught TypeError inside a Promise microtask, bypassing all application-level error handlers and killing the entire Node.js process. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The target application must use undici's WebSocket client API in an affected version (6.7.0 through 6.28.0, 7.0.0 through 7.29.0, or 8.0.0 through 8.10.1) to connect to an endpoint the attacker controls or can intercept. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 7.5 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) accurately reflects the vulnerability: network reachability, no authentication, and no user interaction are required. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade undici to version 6.28.1, 7.29.1, or 8.10.2 - the earliest patched release on each supported branch - as confirmed by GHSA-rfgv-xxqx-mfg5 at https://github.com/nodejs/undici/security/advisories/GHSA-rfgv-xxqx-mfg5. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, audit your application dependencies to identify all use of undici and determine which services use WebSocket functionality, particularly in production systems. …
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Same weakness CWE-248 – Uncaught Exception
View allSame technique Denial Of Service
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External POC / Exploit Code
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