---
id: CVE-2026-34518
aliases:
  - GHSA-966j-vmvw-g2g9
  - PYSEC-2026-2100
title: AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect
summary: AIOHTTP leaks Cookie and Proxy-Authorization headers on cross-origin redirect
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
vendor: aiohttp
product: aiohttp
ecosystem: pip
affected:
  - aiohttp < 3.13.4
patched:
  - aiohttp 3.13.4
published: '2026-04-01'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:51:01.374434696Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-966j-vmvw-g2g9'
references:
  - url: >-
      https://github.com/aio-libs/aiohttp/security/advisories/GHSA-966j-vmvw-g2g9
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34518'
  - url: >-
      https://github.com/aio-libs/aiohttp/commit/5351c980dcec7ad385730efdf4e1f4338b24fdb6
  - url: 'https://github.com/aio-libs/aiohttp'
  - url: 'https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4'
tags:
  - osv
  - pip
epss: 0.00405
epssPercentile: 0.3208
ingestedAt: '2026-07-13T18:57:55.709Z'
---

## Overview

### 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

## Affected packages

- `aiohttp < 3.13.4`

## Remediation

Upgrade to a patched release:

- `aiohttp 3.13.4`