VulnerabilityModified

CVE-2026-1526

The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression.

HIGH 7.5EPSS 1.15%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (1.15%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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.

CVSS 3.1: 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 1.15% probability · 65th percentile
CISA KEV: Not listed
Weakness: CWE-409, CWE-770
Affected: nodejs/undici
Source: ce714d77-add3-4f53-aff5-83d477b104bb

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.