aiohttp: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections
Summary
The server_hostname TLS SNI check can be bypassed when an existing connection is reused.
Impact
If an application makes multiple requests to the same domain, but with different per-request server_hostname parameters, then the later calls may succeed by reusing the existing connection when they should have been rejected due to the TLS SNI check.
Workaround
Disable keep_alive if you need to change the server_hostname check between requests.
Patch: https://github.com/aio-libs/aiohttp/commit/0ca2b6c28a25726527a8b60f25960262a91ed0e0
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:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U- Weakness (CWE)
CWE-297- Platform
- Python (PyPI)
- Package
aiohttp- Disclosed
- 15.06.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-237 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-4m7w-qmgq-4wj5 - 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: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections this entry
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