CVE-2026-1526
Severity CVSS v4.0:
Pending analysis
Type:
Unavailable / Other
Publication date:
12/03/2026
Last modified:
12/03/2026
Description
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.<br />
<br />
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.
Impact
Base Score 3.x
7.50
Severity 3.x
HIGH