CVE-2026-1526 — undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflate Decompression

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
undici / undici	affected < 6.24.0; 7.0.0 < 7.24.0; unaffected 6.24.0: 7.24.0

CWE

CWE-409

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

redhat-SADP

A flaw was found in undici. A remote attacker can exploit this vulnerability by sending a specially crafted compressed frame, known as a "decompression bomb," during permessage-deflate decompression. The undici WebSocket client does not properly limit the size of decompressed data, leading to unbounded memory consumption. This can cause the Node.js process to exhaust available memory, resulting in a denial of service (DoS) where the process crashes or becomes unresponsive.