CVE-2026-1526

undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflate Decompression

Published Mar 12, 2026 CVSS 3.1 · 7.5 High EPSS 1.3% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

Sign in to view the affected projects.

Advisories

Source ID Title
Github GHSA Github GHSA GHSA-vrm6-8vpv-qv8q Undici has Unbounded Memory Consumption in WebSocket permessage-deflate Decompression
History
Type Values Removed Values Added
First Time appeared Nodejs
Nodejs undici
CPEs cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*
Vendors & Products Nodejs
Nodejs undici
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Undici
Undici undici
Vendors & Products Undici
Undici undici
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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Sep 14, 2026, 12:04 PM
Reserved
Jan 28, 2026, 12:05 PM
Status
Modified
Published
Mar 12, 2026, 9:16 PM
Modified
Sep 4, 2026, 1:18 PM
Severity
Important
Public date
Mar 12, 2026, 8:08 PM