CVE-2026-34520
AIOHTTP: C parser (llhttp) accepts null bytes and control characters in response header values - header injection / security bypass
- State
- Published
- Severity
- 2.7 Low
- Published
- Apr 1, 2026
- Updated
- Apr 4, 2026
- Reserved
- Mar 30, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 2.7 Low | 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 | GitHub_M |
| 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H | CISA-ADP |
Weaknesses
- CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
Affected Products
| Product | Versions |
|---|---|
aiohttpaio-libs |
|
References
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