AIOHTTP has HTTP response splitting via \r in reason phrase
Summary
An attacker who controls the reason parameter when creating a Response may be able to inject extra headers or similar exploits.
Impact
In the unlikely situation that an application allows untrusted data to be used in the response's reason parameter, then an attacker could manipulate the response to send something different from what the developer intended.
Patch: https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | aiohttp | < 3.13.4 | 3.13.4 |
References
- https://github.com/aio-libs/aiohttp/releases/tag/v3.13.4
- https://github.com/aio-libs/aiohttp/commit/53b35a2f8869c37a133e60bf1a82a1c01642ba2b
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-mwh4-6h8g-pg8w
- https://nvd.nist.gov/vuln/detail/CVE-2026-34519
- https://github.com/aio-libs/aiohttp
- CVSS 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- Weakness (CWE)
CWE-113- Platform
- Python (PyPI)
- Package
aiohttp- Disclosed
- 01.04.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2101 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-mwh4-6h8g-pg8w - CC BY 4.0
Vulnerability history: aiohttp
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 55
- First → latest
- 02.2021 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 7
- Medium 29
- Low 19
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 6
- 2024: 7
- 2025: 1
- 2026: 40
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AIOHTTP has HTTP response splitting via \r in reason phrase this entry
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