CVE-2026-34516: AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python

Q: How do I fix CVE-2026-34516?

aiohttp: upgrade to 3.13.4. Exact commands for each OS are on this page.

Q: Is CVE-2026-34516 being exploited?

CVE-2026-34516 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-34516 affect?

CVE-2026-34516 affects aiohttp. Severity is high (CVSS 7.5). AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, a response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vu

Q: How urgent is CVE-2026-34516?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-34516 is a high-severity flaw (CVSS 7.5) affecting aiohttp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, a response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability. This issue has been patched in version 3.13.4.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-770
Published	2026-04-01
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: aiohttp

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-01 21:16 UTCPublished CVE record published
2026-10-26 00:10 UTCUpdated Record last modified

aiohttp aiohttp UPGRADE

Affected: < 3.13.4

Fixed in: 3.13.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy aiohttp || rpm -q aiohttp || aiohttp --version

2. UPGRADE to 3.13.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade aiohttp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade aiohttp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-34516?

aiohttp: upgrade to 3.13.4. Exact commands for each OS are on this page.

Is CVE-2026-34516 being exploited?

CVE-2026-34516 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-34516 affect?

CVE-2026-34516 affects aiohttp. Severity is high (CVSS 7.5). AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, a response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vu

How urgent is CVE-2026-34516?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

Related CVEs

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CVE-2026-54277 HIGH 7.5 UPGRADE AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python
CVE-2026-50269 HIGH 7.5 UPGRADE AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python
CVE-2026-54273 HIGH 7.5 UPGRADE AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python

References

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