How severe is CVE-2026-54279?

No CVSS score has been assigned to CVE-2026-54279 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-54279?

CVE-2026-54279 affects the following packages: aiohttp (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-54279?

Update aiohttp to 3.14.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54279 is resolved across your whole dependency graph.

How do I detect CVE-2026-54279 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-54279 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-54279 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-54279 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-54279?

CVE-2026-54279 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 43th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-54279?

CVE-2026-54279 is classified as CWE-665 (CWE-665). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-54279 published, and has it been updated?

CVE-2026-54279 was published on June 22, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-54279 — aiohttp

Fix: aio-libs/aiohttp@a329a7a

CVE-2026-54279 is a CWE-665 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

AIOHTTP: Host-Only Cookies Become Domain Cookies After CookieJar Persistence

Also known asGHSA-2fqr-mr3j-6wp8PYSEC-2026-2112

Published

Jun 22, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54279.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍aiohttp

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

Summary

Host-only cookies that are saved with CookieJar.save() and then restored later with CookieJar.load() lose their host-only status.

Impact

Host-only cookies that have been loaded from disk may get sent to subdomains that previously should have been disallowed.

Patch: https://github.com/aio-libs/aiohttp/commit/a329a7aacad5284f087af36103aff778746da0f2

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`aiohttp`	all versions	3.14.1`pip install --upgrade 'aiohttp==3.14.1'`

Affected Products

1 product · 1 configurations

Application

aiohttpaiohttp

< 3.14.1

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update aiohttp to 3.14.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54279 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Summary Host-only cookies that are saved with ``CookieJar.save()`` and then restored later with ``CookieJar.load()`` lose their host-only status. ### Impact Host-only cookies that have been loaded from disk may get sent to subdomains that previously should have been disallowed. ----- Patch: https://github.com/aio-libs/aiohttp/commit/a329a7aacad5284f087af36103aff778746da0f2

O3 Security · Impact-Aware SCA

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