AIOHTTP: Multipart Header Size Bypass
Priority LOW 36CWE-770Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Partial Red Hat: 8 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-770.
Summary
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 it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00457 39th percentileScored 2026-11-07
Fix Partial aiohttp (aio-libs): 3.13.4aiohttp (PyPI): 3.13.4Red Hat: 8 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| aio-libs | aiohttp | before 3.13.4 | 3.13.4 | Patch available | CNA |
| — | aiohttp (PyPI) | before 3.13.4 | 3.13.4 | Patch available | GHSA-m5qp-6w8w-w647 |
- aiohttp Vendoraio-libs Affected before 3.13.4 Fixed in 3.13.4 Patch available CNA
- aiohttp (PyPI) Vendor— Affected before 3.13.4 Fixed in 3.13.4 Patch available GHSA-m5qp-6w8w-w647
Remediation
- Fix · CNA aiohttp (aio-libs) Fixed in 3.13.4
- Fix · GHSA-m5qp-6w8w-w647 aiohttp (PyPI) Fixed in 3.13.4 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Lightspeed Core | Affected | No fix yet: Fix deferred |
| OpenShift Lightspeed | Affected | No fix yet: Fix deferred |
| Red Hat AI Inference Server | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform 2 | Affected | No fix yet: Fix deferred |
| Red Hat Ansible Automation Platform Ansible Core 2 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux AI (RHEL AI) 3 | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat Satellite 6 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-34516
- 2026-10-03 Alias added: GHSA-m5qp-6w8w-w647
References
Patch 2
More aio-libs vulnerabilities
- TI-2025-38826 aiomysql allows arbitrary access to client files through vulnerability of a malicious MySQL server CVSS 4.0HIGH 8.2
- TI-2024-15436 aiohttp.web.static(follow_symlinks=True) is vulnerable to directory traversal CVSS 3.1HIGH 7.5
- TI-2023-25769 Request smuggling in aiohttp CVSS 3.1HIGH 7.5
- TI-2023-18906 aiohttp vulnerable to HTTP request smuggling CVSS 3.1HIGH 7.5
- TI-2023-26746 aiohttp's ClientSession is vulnerable to CRLF injection via version CVSS 3.1HIGH 7.2
- TI-2026-66145 Multidict: Reference leak in CIMultiDict/MultiDict items-view union and subtraction CVSS 3.1MEDIUM 5.3
Sources
- CVE-2026-34516 · CVE Program
- CVE-2026-34516 · NVD
- FIRST EPSS
- GHSA-m5qp-6w8w-w647 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-34516 · Red Hat security data · CC BY 4.0
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