stale custom cookie host causes cookie leak

Answer in brief

CVE-2026-6276 records a Unknown severity vulnerability in stale custom cookie host causes cookie leak. The current sources do not mark it as known exploited. The current feed maps curl/curl (generic), curl/curl (generic), curl/curl (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 May 13, 2026Updated Sep 15, 2026Source checked Sep 15, 2026First seen by HOL Sep 15, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
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 curl/curl (generic), curl/curl (generic), curl/curl (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
curl/curlgeneric	>=7.71.0 <8.14.2 \|\| >=8.15.0 <8.16.1 \|\| >=8.17.0 <8.20.0	8.14.2, 8.16.1, 8.20.0
curl/curlgeneric	>=e15e51384a423be31318b3c9c7d612a1aae661fd <3a19987a87f393d9394fe5acc7643f6c263c92db	3a19987a87f393d9394fe5acc7643f6c263c92db
curl/curlgeneric	8.19.0 \|\| 8.18.0 \|\| 8.17.0 \|\| 8.16.0 \|\| 8.15.0 \|\| 8.14.1 \|\| 8.14.0 \|\| 8.13.0 \|\| 8.12.1 \|\| 8.12.0 \|\| 8.11.1 \|\| 8.11.0 \|\| 8.10.1 \|\| 8.10.0 \|\| 8.9.1 \|\| 8.9.0 \|\| 8.8.0 \|\| 8.7.1 \|\| 8.7.0 \|\| 8.6.0 \|\| 8.5.0 \|\| 8.4.0 \|\| 8.3.0 \|\| 8.2.1 \|\| 8.2.0 \|\| 8.1.2 \|\| 8.1.1 \|\| 8.1.0 \|\| 8.0.1 \|\| 8.0.0 \|\| 7.88.1 \|\| 7.88.0 \|\| 7.87.0 \|\| 7.86.0 \|\| 7.85.0 \|\| 7.84.0 \|\| 7.83.1 \|\| 7.83.0 \|\| 7.82.0 \|\| 7.81.0 \|\| 7.80.0 \|\| 7.79.1 \|\| 7.79.0 \|\| 7.78.0 \|\| 7.77.0 \|\| 7.76.1 \|\| 7.76.0 \|\| 7.75.0 \|\| 7.74.0 \|\| 7.73.0 \|\| 7.72.0 \|\| 7.71.1 \|\| 7.71.0	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for curl/curl, curl/curl, curl/curl.
Review the reported fix. Update curl/curl to 8.14.2; curl/curl to 3a19987a87f393d9394fe5acc7643f6c263c92db if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 13, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 15, 2026

Sources and claim methodology

Upstream source description

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

Quoted source text, attributed separately from HOL analysis.