HTTP response splitting in aio-libs aiohttp
Priority LOW 20CWE-113Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- Partial Red Hat: 8 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat.
Summary
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser (the default for most installs) accepted null bytes and control characters in response headers. This issue has been patched in version 3.13.4.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00479 41st 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-63hf-3vf5-4wqf |
- 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-63hf-3vf5-4wqf
Remediation
- Fix · CNA aiohttp (aio-libs) Fixed in 3.13.4
- Fix · GHSA-63hf-3vf5-4wqf aiohttp (PyPI) Fixed in 3.13.4 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Low. 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-2026-34520
- 2026-10-03 Alias added: GHSA-63hf-3vf5-4wqf
- 2026-10-25 EPSS moved to the below the 50th percentile
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-2026-34520 · CVE Program
- CVE-2026-34520 · NVD
- FIRST EPSS
- GHSA-63hf-3vf5-4wqf · GitHub Advisory Database · CC BY 4.0
- CVE-2026-34520 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences