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.

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Fixes

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History

Fri, 13 Mar 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-770
References
Metrics threat_severity

None

threat_severity

Important


Thu, 12 Mar 2026 20:30:00 +0000

Type Values Removed Values Added
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. 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.
Title undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflate Decompression
Weaknesses CWE-409
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-03-12T20:08:05.950Z

Reserved: 2026-01-28T12:05:07.017Z

Link: CVE-2026-1526

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-03-12T21:16:23.933

Modified: 2026-03-12T21:16:23.933

Link: CVE-2026-1526

cve-icon Redhat

Severity : Important

Publid Date: 2026-03-12T20:08:05Z

Links: CVE-2026-1526 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses