CVE-2026-34516

AIOHTTP: Multipart Header Size Bypass

HIGH
7.5
CVSS Score
Published: April 1, 2026 at 08:13 PM UTC
Updated: October 26, 2026 at 12:10 AM UTC
2 products affected across 2 vendorsAiohttpAiohttp

Using aiohttp by aio-libs?

Get instant alerts when new vulnerabilities affect aiohttp - before attackers find them.

Real-time alertsTrack your software stackFree plan available
Severity
HIGH7.5
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.13.4
v < 3.13.4
Affected range stops below 3.13.4, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-770

Get alerted

Stop reading CVE feeds looking for your own stack

Track the products you run and VulnTracker tells you when a new CVE affects them — with what is known about fixing it, and nothing about the rest.

Free plan, no card