Improper access control in aiohttp - CVE-2026-54279
Published: June 9, 2026
Vulnerability identifier: #VU133996
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-54279
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: aio-libs
Affected software:
aiohttp
aiohttp
Detailed vulnerability description
The vulnerability allows a remote attacker to cause cookies intended for a single host to be sent to subdomains.
The vulnerability exists due to improper cookie scope handling in CookieJar persistence when saving and restoring host-only cookies with CookieJar.save() and CookieJar.load(). A remote attacker can cause a restored host-only cookie to be treated as a domain cookie to cause cookies intended for a single host to be sent to subdomains.
The issue occurs after cookies are persisted to disk and later reloaded.
How to mitigate CVE-2026-54279
Install security update from vendor's website.