GHSA-4m7w-qmgq-4wj5 CVE-2026-54275 PYSEC-2026-237
aiohttp: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections
- Severity
- 0.0 / 10
- High · CVSS 4.0
- Exploit chance (EPSS)
- 0.47%
- Chance of exploitation in the next 30 days. Higher than 40.70% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-297 Improper Validation of Certificate with Host Mismatch
- Fix
3.14.1- Upgrade aiohttp to this version or later
Description
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 versions
PyPI
| Package | Vulnerable | Fixed in |
|---|---|---|
| aiohttp | < 3.14.1 |
3.14.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
aiohttp PyPI → 3.14.1
- pip
pip install --upgrade "aiohttp>=3.14.1"- poetry
poetry add "aiohttp>=3.14.1"- uv
uv add "aiohttp>=3.14.1"
Severity breakdown
CVSS 4.0 0.0
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
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- Low
- Integrity (vulnerable system)
- Low
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
- Exploit maturity
- Unreported
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-297: Improper Validation of Certificate with Host Mismatch
The product communicates with a host that provides a certificate, but the product does not properly ensure that the certificate is actually associated with that host.
How to prevent it
- Architecture and Design: Fully check the hostname of the certificate and provide the user with adequate information about the nature of the problem and how to proceed.
- Implementation: If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
References
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-pqxq-w44r-73xw AIOHTTP: Pure-Python parser request smuggling | Medium | Also affects aiohttp |
| GHSA-gx76-c99x-2c96 AIOHTTP: Cookie from subdomain can remove Host-Only Scope from existing cookies | Low | Also affects aiohttp |
| GHSA-f9xw-jh8m-3mwq AIOHTTP: Absolute-form request targets can spoof Request.scheme | Medium | Also affects aiohttp |
| GHSA-9xw5-w5jj-pvcg AIOHTTP: File descriptor exhaustion in multipart requests | High | Also affects aiohttp |
| GHSA-6cjc-53gc-5rqm AIOHTTP: Connector pool exhaustion via Max-Age overflow | Medium | Also affects aiohttp |
| GHSA-5wr8-gcqf-gqf3 aiohttp server lacks an initial request/header timeout | High | Also affects aiohttp |
| GHSA-494j-54xm-rwp3 AIOHTTP: Secure attribute not enforced for shared cookie | Medium | Also affects aiohttp |
| GHSA-2g87-pp6c-29x5 aiohttp: Multiple instances of excessive or unbounded memory/CPU use | High | Also affects aiohttp |
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