CVE-2026-109932

undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering

Workarounds

None.

undici's WebSocket client (including Node.js's bundled globalThis.WebSocket) can be driven to exhaust process memory by a malicious or compromised WebSocket server. For every PING frame received, the receiver automatically writes a PONG response to the socket and ignores the false return value from socket.write(), which is a backpressure signal, so a server that streams small PING frames while never reading the client's PONGs makes the outbound write queue and heap grow without bound until the Node.js process runs out of memory and terminates. The attack is remote and unauthenticated, needs only a normal WebSocket connection, and is asymmetric: small inbound PINGs produce a much larger retained outbound queue. Availability is the only impact. undici 5.x, 6.x, 7.x, and 8.x are affected; the WebSocket client was introduced in 5.15.0.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-109932 has a CVSS score of 5.9 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.29.1, 7.30.1, 8.12.2); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

Upgrade to 6.29.1, 7.30.1, or 8.12.2, which pause WebSocket frame parsing when the automatic PONG response hits socket backpressure and resume on drain, bounding the outbound queue.

1. What is CVE-2026-109932? CVE-2026-109932 is a medium-severity uncontrolled resource consumption vulnerability in undici (npm), affecting versions >= 5.15.0, < 6.29.1. It is fixed in 6.29.1, 7.30.1, 8.12.2. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2026-109932? CVE-2026-109932 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of undici are affected by CVE-2026-109932? undici (npm) versions >= 5.15.0, < 6.29.1 is affected.
4. Is there a fix for CVE-2026-109932? Yes. CVE-2026-109932 is fixed in 6.29.1, 7.30.1, 8.12.2. Upgrade to this version or later.
5. Is CVE-2026-109932 exploitable, and should I be worried? Whether CVE-2026-109932 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-109932 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-109932?
   • Upgrade undici to 6.29.1 or later
   • Upgrade undici to 7.30.1 or later
   • Upgrade undici to 8.12.2 or later

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