CVE-2026-54279: aio-libs aiohttp host-only cookie scope loss in CookieJar

CVE-2026-54279 · Severity: medium · CVSS 4 · Published 2026-06-22

AIOHTTP is a popular Python library used by developers to build web servers and clients. A flaw in how it handles saved login or session information (cookies) means that certain security restrictions are lost when the application is restarted. This could allow sensitive session data intended for a specific website to be accidentally sent to its subdomains, potentially leading to unauthorized access if those subdomains are untrusted.

Technologies: aiohttp (PyPI). Vendors: PyPI.

Quick answers

Is CVE-2026-54279 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-54279 being exploited in the wild.
How severe is CVE-2026-54279?
Medium severity, with a CVSS score of 4, published 22 June 2026.
Which products and versions are affected?
aiohttp (PyPI) <= 3.14.0, ECOSYSTEM:introduced=0,fixed=3.14.1.
Is there a fix for CVE-2026-54279?
Yes. aiohttp (PyPI): upgrade to 3.14.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-54279 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-54279?
Check whether you run aiohttp (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • aiohttp (PyPI): upgrade to 3.14.1 or later
    pip install "aiohttp>=3.14.1"

Technical details

A vulnerability exists in the CookieJar component of aiohttp where cookies saved via CookieJar.save() and restored via CookieJar.load() lose their host-only attribute. By default, cookies without a 'Domain' attribute should only be sent to the exact host that issued them; however, this bug causes reloaded cookies to be treated as domain cookies, making them available to all subdomains. An attacker who controls a subdomain could potentially receive sensitive cookies intended only for the parent domain. This issue is fixed in version 3.14.1, which also ensures absolute expiration deadlines are persisted and improves cookie acceptance rules during loading.

Affected products

  • aio-libs aiohttp <= 3.14.0

Identifiers

  • CVE-2026-54279
  • GHSA-2fqr-mr3j-6wp8
  • PYSEC-2026-2112

Timeline

  • 2026-06-07: patched: Fix committed to repository
  • 2026-06-08: advisory: GitHub Security Advisory published
  • 2026-06-22: disclosed: NVD publication date

References

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