EUVD-2026-11699
GHSA-vrm6-8vpv-qv8q
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4Description
The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive. The vulnerability exists in the PerMessageDeflate.decompress() method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold.
Analysis
Node.js undici WebSocket client denial-of-service via decompression bomb in permessage-deflate processing allows remote attackers to crash or hang affected processes through unbounded memory consumption. An attacker controlling a malicious WebSocket server can send specially crafted compressed frames that expand to extremely large sizes in memory without triggering any decompression limits. …
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Remediation
Within 24 hours: Identify all systems and applications using undici WebSocket functionality and assess exposure to untrusted WebSocket sources. Within 7 days: Implement compensating controls such as connection rate limiting, memory usage monitoring, and disable permessage-deflate compression if not operationally critical. …
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