undici vulnerable to HTTP response queue poisoning via keep-alive socket reuse (CVE-2026-6733)

undici vulnerable to HTTP response queue poisoning via keep-alive socket reuse (CVE-2026-6733) | HOL Guard CVE

Why this deserves its current priority

CVSS is 3.7. 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 (npm), undici (npm), undici (npm), undici (npm) and additional mapped packages. Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
undicinpm	<6.27.0	6.27.0
undicinpm	>=7.0.0,<7.28.0	7.28.0
undicinpm	>=8.0.0,<8.5.0	8.5.0
undicinpm	>=0 <6.27.0	6.27.0
undicinpm	>=7.0.0 <7.28.0	7.28.0
undicinpm	>=8.0.0 <8.5.0	8.5.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for undici, undici, undici.
Review the reported fix. Update undici to 6.27.0; undici to 7.28.0; undici to 8.5.0; undici to 6.27.0; undici to 7.28.0; undici to 8.5.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jun 17, 2026
Evidence: source:ghsa:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:ghsa:source_dates:source-dates:record
First seen by HOL
Jun 19, 2026

Sources and claim methodology

Upstream source description

## Impact Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests. This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse. ## Patches Upgrade to undici v6.27.0, v7.28.0 or v8.5.0. ## Workarounds Disable keep-alive connection reuse by setting `keepAliveTimeout: 0` on the Client or Pool.

Quoted source text, attributed separately from HOL analysis.