CVE-2026-54279: aiohttp Host-Only Cookies Become Domain Cookies Vulnerability

LOW
Advisory Identifier: GHSA-2fqr-mr3j-6wp8
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CWE-665
Published
Advisory Summary

CVE-2026-54279 is a LOW host-only cookies become domain cookies vulnerability (CWE-665: Improper Initialization) affecting aiohttp libraries in the PyPI ecosystem. The issue involves host-only cookies become domain cookies after cookiejar persistence. Remediation is available by upgrading affected packages to version 3.14.1.

CVE-2026-54279 at a Glance

CVE Identifier CVE-2026-54279
GHSA Identifier GHSA-2fqr-mr3j-6wp8
Severity LOW
CVSS v3.1 Base Score N/A
CWE Classification CWE-665: Improper Initialization
Affected Product aiohttp
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-54279

To remediate this vulnerability, upgrade all affected aiohttp dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

aiohttp fixed: 3.14.1 
pip install aiohttp>=3.14.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show aiohttp

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-54279, inspect your installed packages using pip:

pip show aiohttp

Analyze the terminal output to locate any version of aiohttp in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.14.1), your application is affected.

Note: The pip show aiohttp command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-665: Improper Initialization, where the product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. In aiohttp, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### 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

CVE-2026-54279 Affected aiohttp Versions

1 component(s)
Fixed Versions:
3.14.1
Product / Package Ecosystem Affected Versions Fixed Version
aiohttp
pypi/aiohttp
PyPI
< 3.14.1
3.14.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/aio-libs/aiohttp/security/advisories/GHSA-2fqr-mr3j-6wp8
aiohttp Source Repository REPOSITORY
https://github.com/aio-libs/aiohttp

Frequently Asked Questions

What is CVE-2026-54279?
CVE-2026-54279 is a security vulnerability in aiohttp involving Host-Only Cookies Become Domain Cookies After CookieJar Persistence under CWE-665: Improper Initialization.
Which aiohttp versions are affected?
Affected versions include releases prior to 3.14.1 across affected packages: aiohttp.
What version fixes CVE-2026-54279?
Upgrading to 3.14.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is aiohttp affected?
Yes, aiohttp is affected in releases prior to 3.14.1. Upgrade your dependency to 3.14.1 or later.
What CWE is associated with CVE-2026-54279?
CVE-2026-54279 is classified under CWE-665: Improper Initialization (The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used.).
How can I check PyPI dependencies for CVE-2026-54279?
Run the dependency tree command: 'pip show aiohttp'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2fqr-mr3j-6wp8",
  "modified" : "2026-06-15T20:08:51Z",
  "published" : "2026-06-15T20:08:51Z",
  "aliases" : [ "CVE-2026-54279" ],
  "summary" : "aiohttp: Host-Only Cookies Become Domain Cookies After CookieJar Persistence",
  "details" : "### Summary\n\nHost-only cookies that are saved with ``CookieJar.save()`` and then restored later with ``CookieJar.load()`` lose their host-only status.\n\n### Impact\n\nHost-only cookies that have been loaded from disk may get sent to subdomains that previously should have been disallowed.\n\n-----\n\nPatch: https://github.com/aio-libs/aiohttp/commit/a329a7aacad5284f087af36103aff778746da0f2",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N/E:U"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "aiohttp"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.14.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 3.14.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/aio-libs/aiohttp/security/advisories/GHSA-2fqr-mr3j-6wp8"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/aio-libs/aiohttp"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-665" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-15T20:08:51Z",
    "nvd_published_at" : null
  }
}