AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect (CVE-2026-34518) | HOL Guard CVE

Medium · CVSS 5.3CVE-2026-34518GHSA-966J-VMVW-G2G9

AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect

Answer in brief

CVE-2026-34518 records a Medium severity (CVSS 5.3) vulnerability in AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect. The current sources do not mark it as known exploited. The current feed maps aiohttp (pypi). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

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

Published Apr 1, 2026Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Sep 10, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.3
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 5.3. 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 aiohttp (pypi). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
aiohttppypi	>=0 <3.13.4	3.13.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for aiohttp.
Review the reported fix. Update aiohttp to 3.13.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Apr 1, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

Upstream source description

### Summary When following redirects to a different origin, aiohttp drops the Authorization header, but retains the Cookie and Proxy-Authorization headers. ### Impact The Cookie and Proxy-Authorizations headers could contain sensitive information which may be leaked to an unintended party after following a redirect. ----- Patch: https://github.com/aio-libs/aiohttp/commit/5351c980dcec7ad385730efdf4e1f4338b24fdb6

Quoted source text, attributed separately from HOL analysis.