CVE-2026-9675

A flaw was found in undici. A malicious WebSocket server could exploit this vulnerability by sending fragmented messages that individually meet size limits but collectively exceed them. This can lead to unbounded memory growth in the client process, resulting in memory exhaustion and a denial of service (DoS).

This is rated Moderate by Red Hat (CVSS 5.9) because successful exploitation requires the undici WebSocket client to connect to an attacker-controlled server (AC:H), which is unlikely in typical Red Hat product deployments where WebSocket endpoints are trusted internal services. No Red Hat product is affected — all streams shipping undici bundle versions 5.x through 7.x, which are outside the vulnerable range of 8.0.0 to 8.4.x. The vulnerable code path (unbounded WebSocket frame accumulation) was introduced in undici 8.0.0 and is not present in earlier major versions.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Red Hat products that bundle the undici HTTP client ship versions 5.x, 6.x, and 7.x, which do not contain the vulnerable WebSocket frame accumulation code path introduced in undici 8.0.0. No Red Hat product streams are affected by this vulnerability. Users who have manually installed undici 8.x outside of Red Hat-provided packages should upgrade to undici 8.5.0 or later to fully resolve this issue.