Description
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.
Published: 2026-04-01
Score: 2.7 Low
EPSS: < 1% Very Low
KEV: No
Impact: Header Injection / Security Bypass
Action: Patch
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-63hf-3vf5-4wqf AIOHTTP's C parser (llhttp) accepts null bytes and control characters in response header values - header injection/security bypass
History

Thu, 16 Apr 2026 16:30:00 +0000

Type Values Removed Values Added
First Time appeared Aiohttp
Aiohttp aiohttp
CPEs cpe:2.3:a:aiohttp:aiohttp:*:*:*:*:*:*:*:*
Vendors & Products Aiohttp
Aiohttp aiohttp

Sat, 04 Apr 2026 05:00:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H'}


Thu, 02 Apr 2026 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Aio-libs
Aio-libs aiohttp
Vendors & Products Aio-libs
Aio-libs aiohttp

Thu, 02 Apr 2026 00:15:00 +0000

Type Values Removed Values Added
Weaknesses CWE-1286
References
Metrics threat_severity

None

cvssV3_1

{'score': 3.7, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N'}

threat_severity

Low


Wed, 01 Apr 2026 23:45:00 +0000

Type Values Removed Values Added
Description 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.
Title AIOHTTP: C parser (llhttp) accepts null bytes and control characters in response header values - header injection / security bypass
Weaknesses CWE-113
References
Metrics cvssV4_0

{'score': 2.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-04T03:13:48.418Z

Reserved: 2026-03-30T16:03:31.047Z

Link: CVE-2026-34520

cve-icon Vulnrichment

Updated: 2026-04-04T03:13:43.374Z

cve-icon NVD

Status : Analyzed

Published: 2026-04-01T21:17:00.333

Modified: 2026-04-16T16:24:37.047

Link: CVE-2026-34520

cve-icon Redhat

Severity : Low

Publid Date: 2026-04-01T20:27:48Z

Links: CVE-2026-34520 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-04-02T20:16:39Z

Weaknesses