undici vulnerable to Denial of Service via unhandled error in WebSocket permessage-deflate decompression (CVE-2026-85024) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-85024

undici vulnerable to Denial of Service via unhandled error in WebSocket permessage-deflate decompression

Answer in brief

CVE-2026-85024 records a Unknown severity vulnerability in undici vulnerable to Denial of Service via unhandled error in WebSocket permessage-deflate decompression. The current sources do not mark it as known exploited. The current feed maps undici/undici (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 4, 2026Updated Sep 4, 2026Source checked Sep 4, 2026First seen by HOL Sep 4, 2026Material review Sep 4, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps undici/undici (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
undici/undicigeneric	>=6.25.0 <6.28.1 \|\| >=7.28.0 <7.29.1 \|\| >=8.1.0 <8.10.2	6.28.1, 7.29.1, 8.10.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for undici/undici.
Review the reported fix. Update undici/undici to 6.28.1 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 4, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 4, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 4, 2026

Sources and claim methodology

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.