---
id: "CVE-2026-111749"
kind: "vulnerability"
aliases: ["CVE-2026-111749", "GHSA-gx76-c99x-2c96"]
title: "AIOHTTP: Cookie from subdomain can remove Host-Only Scope from existing cookies"
severity: "low"
cvss: 2.3
epss: 0.002940000034868717
exploited: false
status: "open"
category: "package"
products: [{"name": "aiohttp", "fixed": ["3.14.4"], "affected": "<= 3.14.3", "ecosystem": "pypi"}]
ecosystems: ["pypi"]
tags: ["aiohttp", "cookie-handling", "cwe-565", "package", "python"]
not_affected_if: ["aiohttp-4.14.4-or-later", "no-untrusted-subdomains", "static-export"]
published_at: "2026-10-19T17:17:04+00:00"
first_seen_at: "2026-10-23T19:11:32+00:00"
updated_at: "2026-10-23T21:57:18+00:00"
sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-gx76-c99x-2c96", "first_seen_at": "2026-10-23T19:11:32+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-111749", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# AIOHTTP: Cookie from subdomain can remove Host-Only Scope from existing cookies

AIOHTTP's cookie jar lets a subdomain remove the Host-Only flag from an existing cookie set for a parent domain, so the cookie becomes sent to the parent domain and its other subdomains. An attacker controlling a subdomain can strip that protection from cookies held by a client using the library.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- pypi:aiohttp affected <= 3.14.3 fixed 3.14.4

## How to check

Check whether the project pins aiohttp with pip show aiohttp or pip freeze | grep -i aiohttp and whether the version is 3.14.3 or lower.

## Fix

Upgrade aiohttp to 3.14.4 or later.

## Timeline

- 2026-10-23T19:11:32+00:00 ghsa https://github.com/advisories/GHSA-gx76-c99x-2c96
- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-111749

## From the sources

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.4, Host-Only scope on an existing parent-domain cookie can be removed by a subdomain. A user who accesses an untrusted subdomain can consequently have host-only protections stripped from cookies, although impact is limited when applications do not reflect those cookies to a browser. This issue is fixed in version 3.14.4.

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