aiohttp: C HTTP Parser Bypasses max_line_size for Fragmented Lines
Summary
It is possible to bypass the max_line_size check in parts of an HTTP request in the C parser.
Impact
If using the optimised C parser (the default in pre-built wheels), then an attacker may be able to send oversized lines through the HTTP parser and use an excessive amount of memory, potentially leading to DoS.
Patch: https://github.com/aio-libs/aiohttp/commit/5ab61bb4cd88f19b712f12c7c9295fe262bf804d
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | aiohttp | < 3.14.1 | 3.14.1 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U- Weakness (CWE)
CWE-770- Platform
- Python (PyPI)
- Package
aiohttp- Disclosed
- 15.06.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-2110 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-63hw-fmq6-xxg2 - 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: C HTTP Parser Bypasses max_line_size for Fragmented Lines this entry
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