# CVE-2026-34514: aiohttp — Fixed in 3.13.4

🐍 PyPI

Not in CISA KEV

# CVE-2026-34514 — aiohttp

[Fix: aio-libs/aiohttp@9a6ada9](https://github.com/aio-libs/aiohttp/commit/9a6ada97e2c6cf1ce31727c6c9fcea17c21f6f06)

CVE-2026-34514 is a CWE-113 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

AIOHTTP: CRLF injection in multipart part content type header construction

Also known as[GHSA-2vrm-gr82-f7m5](/vulnerability/GHSA-2vrm-gr82-f7m5)PYSEC-2026-2096

Published

Apr 1, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   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-2026-34514.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs26th percentile — riskier than 26% of all scored CVEsHighest risk

0.00%0.30%0.60%0.90%0.0%0.3%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.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

An attacker who controls the `content_type` parameter in aiohttp could use this to inject extra headers or similar exploits.

#### Impact

If an application allows untrusted data to be used for the multipart `content_type` parameter when constructing a request, an attacker may be able to manipulate the request to send something other than what the developer intended.

* * *

Patch: [https://github.com/aio-libs/aiohttp/commit/9a6ada97e2c6cf1ce31727c6c9fcea17c21f6f06](https://github.com/aio-libs/aiohttp/commit/9a6ada97e2c6cf1ce31727c6c9fcea17c21f6f06)

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

🐍PyPI

`aiohttp` 

all versions

3.13.4`pip install --upgrade 'aiohttp==3.13.4'`

## Affected Products

1 product · 1 configurations

Application

`aiohttp`aiohttp

< 3.13.4

range

## Detection & mitigation playbook

Open-source dependency

1.  ### 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.
    
2.  ### Fix
    
    Update aiohttp to 3.13.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34514 is resolved across your whole dependency graph.
    
3.  ### 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.
    

## 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 HatModerate

Workaround published by Red Hat

> Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: [Red Hat security advisory for CVE-2026-34514](https://access.redhat.com/security/cve/cve-2026-34514) (CC BY 4.0)

## Frequently Asked Questions

\### Summary An attacker who controls the \`content\_type\` parameter in aiohttp could use this to inject extra headers or similar exploits. ### Impact If an application allows untrusted data to be used for the multipart \`content\_type\` parameter when constructing a request, an attacker may be able to manipulate the request to send something other than what the developer intended. ----- Patch: https://github.com/aio-libs/aiohttp/commit/9a6ada97e2c6cf1ce31727c6c9fcea17c21f6f06

O3 Security · Impact-Aware SCA

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