undici bundles a WebSocket client whose permessage-deflate size-limit cleanup removes all listeners from the internal zlib inflate stream, including its error listener, while that stream can still emit. When a remote peer sends a compressed payload that crosses the built-in 128 MiB decompressed-payload limit and then contains a malformed DEFLATE byte, the inflate stream emits a data error with no listener attached, which Node.js treats as a fatal unhandled error and terminates the entire process. Exploitation is remote and unauthenticated, requires no application mistake, and is asymmetric, since roughly 130 KB on the wire expands past the limit and crashes the process, and reconnecting can repeat the crash. This affects undici versions from 6.25.0 up to 6.28.1, from 7.28.0 up to 7.29.1, and from 8.1.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.

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Fixes

Solution

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Workaround

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History

Sat, 05 Sep 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-431
References
Metrics threat_severity

None

threat_severity

Moderate


Fri, 04 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Description undici bundles a WebSocket client whose permessage-deflate size-limit cleanup removes all listeners from the internal zlib inflate stream, including its error listener, while that stream can still emit. When a remote peer sends a compressed payload that crosses the built-in 128 MiB decompressed-payload limit and then contains a malformed DEFLATE byte, the inflate stream emits a data error with no listener attached, which Node.js treats as a fatal unhandled error and terminates the entire process. Exploitation is remote and unauthenticated, requires no application mistake, and is asymmetric, since roughly 130 KB on the wire expands past the limit and crashes the process, and reconnecting can repeat the crash. This affects undici versions from 6.25.0 up to 6.28.1, from 7.28.0 up to 7.29.1, and from 8.1.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.
Title undici vulnerable to Denial of Service via unhandled error in WebSocket permessage-deflate decompression
Weaknesses CWE-248
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-09-04T19:30:54.293Z

Reserved: 2026-09-02T19:57:23.011Z

Link: CVE-2026-85024

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-09-04T17:17:02.590

Modified: 2026-09-04T20:17:31.137

Link: CVE-2026-85024

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-04T16:20:34Z

Links: CVE-2026-85024 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-09-04T21:00:13Z

Weaknesses