What’s Vulnerable › Vulnerabilities

CVE-2026-111749: AIOHTTP: Cookie from subdomain can remove Host-Only Scope from existing cookies

• Severity: low (CVSS 2.3 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-19 · updated 2026-10-22
• Weakness: CWE-565

Description

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.

Affected products

• Pypi Aiohttp: before 3.14.4; 0.1, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 0.12.0 (+304) — fixed in 3.14.4
• aio-libs aiohttp: before 3.14.4

How to fix

Upgrade to a fixed version: Pypi Aiohttp 3.14.4. Check the vendor advisory for mitigations.

References

• https://github.com/aio-libs/aiohttp/commit/6a07c171ef9f3be583e2907dcd1931372efca8d6
• https://github.com/aio-libs/aiohttp/releases/tag/v3.14.4
• https://github.com/aio-libs/aiohttp/security/advisories/GHSA-gx76-c99x-2c96

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