How severe is CVE-2026-34993?

CVE-2026-34993 has a CVSS score of 6.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-34993?

CVE-2026-34993 affects the following packages: aiohttp (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-34993?

Update aiohttp to 3.14.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34993 is resolved across your whole dependency graph.

How do I detect CVE-2026-34993 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-2026-34993 if there is no patch (or I can't update yet)?

Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Is CVE-2026-34993 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-34993 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-2026-34993?

CVE-2026-34993 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 40th 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-2026-34993?

CVE-2026-34993 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-34993 published, and has it been updated?

CVE-2026-34993 was published on June 2, 2026 and was last updated on September 18, 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

MEDIUM severity

CVE-2026-34993 — aiohttp

MEDIUMFix: aio-libs/aiohttp@dcf40f3

CVE-2026-34993 is a medium-severity (CVSS 6.4) Deserialization of Untrusted Data vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

AIOHTTP Vulnerable to Deserialization of Untrusted Data

Also known asGHSA-jg22-mg44-37j8PYSEC-2026-2104

Published

Jun 2, 2026

Updated

Sep 18, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 27, 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-2026-34993.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs40th percentile — riskier than 40% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2026-34993 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

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

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.14.0, using CookieJar.load() with untrusted input may allow arbitrary code execution. Most applications using this function will be doing so with the user's own data, so this is unlikely to affect many applications. Version 3.14.0 patches the issue. If an application does allow attacker controlled files to be loaded, a workaround on older releases would be to sanitize the files before loading.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`aiohttp`	all versions	3.14.0`pip install --upgrade 'aiohttp==3.14.0'`

Affected Products

1 product · 1 configurations

Application

aiohttpaiohttp

< 3.14.0

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 3.14.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34993 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

This is an Important flaw in AIOHTTP, a Python asynchronous HTTP framework, due to potential arbitrary code execution. The vulnerability arises when applications load untrusted input into the `CookieJar.load()` function. Exploitation requires an application to be configured to process attacker-controlled files, which…

Workaround published by Red Hat

Applications using AIOHTTP that are configured to load untrusted files via the `CookieJar.load()` function should implement input sanitization prior to loading. This prevents the injection of malicious code.

Source: Red Hat security advisory for CVE-2026-34993 (CC BY 4.0)

Product	Fixed in	Advisory
Red Hat Ansible Automation Platform 2.5 for RHEL 8	`python3.12-aiohttp-0:3.14.1-2.el8ap`	RHSA-2026:50319
Red Hat Ansible Automation Platform 2.5 for RHEL 8	`automation-controller-0:4.6.32-1.el8ap`	RHSA-2026:59135
Red Hat Ansible Automation Platform 2.6 for RHEL 9	`python3.12-aiohttp-0:3.14.1-2.el9ap`	RHSA-2026:50336
Red Hat Ansible Automation Platform 2.6 for RHEL 9	`automation-controller-0:4.7.16-1.el9ap`	RHSA-2026:59136
Red Hat Satellite 6.16 for RHEL 8	`python-aiohttp-0:3.14.3-1.el8pc`	RHSA-2026:63327
Red Hat Satellite 6.17 for RHEL 9	`ansible-core-1:2.16.19-1.el9sat`	RHSA-2026:63387
Red Hat Satellite 6.18 for RHEL 9	`pulpcore-obsolete-packages-0:1.3.1-5.el9pc`	RHSA-2026:63386
Red Hat Satellite 6.19 for RHEL 9	`python3.12-aiohttp-0:3.14.3-1.el9pc`	RHSA-2026:63385

Frequently Asked Questions

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.14.0, using ``CookieJar.load()`` with untrusted input may allow arbitrary code execution. Most applications using this function will be doing so with the user's own data, so this is unlikely to affect many applications. Version 3.14.0 patches the issue. If an application does allow attacker controlled files to be loaded, a workaround on older releases would be to sanitize the files before loading.

O3 Security · Impact-Aware SCA

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