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Python aiohttp: Prior to 3.14.1, the server_hostname TLS SNI check can be bypassed when an existing connection is reused. (CVE-2026-54275)

0
Medium
VulnerabilityCVE-2026-54275gcveosvubuntu-cve-2026-54275cve-2026-54275ubuntu-pro-16-04-ltsubuntu-pro-18-04-ltsubuntu-pro-20-04-ltsubuntu-pro-22-04-ltsubuntu-pro-24-04-ltsubuntu-25-10ubuntu-26-10ubuntu-pro-26-04-lts
Published: 06/22/2026 (06/22/2026, 18:16:00 UTC)
Source: GCVE Database
Product: python-aiohttp

Description

Python aiohttp versions prior to 3.14.1 contain a vulnerability where the server_hostname TLS SNI check can be bypassed when an existing connection is reused. This allows later requests with different server_hostname parameters to reuse a TLS connection that should have been rejected. The issue is fixed in version 3.14.1.

CVSS v3.1

Score 7.5high

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected software

Ubuntu:Pro:16.04:LTSmore threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=esm-apps-legacy/xenial
Affected versions
=0.17.2-1=0.17.4-1=0.17.4-1build1=0.20.2-1=0.20.2-1ubuntu0.1~esm1
Ubuntu:Pro:18.04:LTSmore threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=esm-apps/bionic
Affected versions
=2.2.3-1build1=2.2.3-2=2.3.6-1=3.0.1-1=3.0.1-1ubuntu0.1~esm1=3.0.1-1ubuntu0.1~esm4=3.0.1-1ubuntu0.1~esm5=3.0.1-1ubuntu0.1~esm6=3.0.1-1ubuntu0.1~esm7
Ubuntu:Pro:20.04:LTSmore threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=esm-apps/focal
Affected versions
=3.5.4-1=3.5.4-1build1=3.6.1-1=3.6.2-1=3.6.2-1build1=3.6.2-1ubuntu0.1~esm1=3.6.2-1ubuntu1=3.6.2-1ubuntu1+esm1=3.6.2-1ubuntu1+esm3=3.6.2-1ubuntu1+esm4=3.6.2-1ubuntu1+esm5=3.6.2-1ubuntu1+esm6
Ubuntu:Pro:22.04:LTSmore threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=esm-apps/jammy
Affected versions
=3.7.4-1=3.7.4-1build2=3.8.1-3=3.8.1-4=3.8.1-4build1=3.8.1-4ubuntu0.2=3.8.1-4ubuntu0.2+esm1=3.8.1-4ubuntu0.2+esm2=3.8.1-4ubuntu0.2+esm3
Ubuntu:Pro:24.04:LTSmore threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=esm-apps/noble
Affected versions
=3.8.4-1=3.9.1-1=3.9.1-1build1=3.9.1-1ubuntu0.1=3.9.1-1ubuntu0.1+esm1=3.9.1-1ubuntu0.1+esm2=3.9.1-1ubuntu0.1+esm3
Ubuntu:25.10more threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=questing
Affected versions
=3.10.11-1build1=3.11.16-1=3.11.16-1ubuntu0.1
Ubuntu:26.10more threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=stonking
Affected versions
=3.13.3-3ubuntu1=3.14.1-4=3.14.1-5=3.14.3-1
Ubuntu:Pro:26.04:LTSmore threats →ghsa
python-aiohttp
pkg:deb/ubuntu/python-aiohttp?arch=source&distro=esm-apps/resolute
Affected versions
=3.11.16-1=3.13.1-1=3.13.3-3=3.13.3-3ubuntu1=3.13.3-3ubuntu1+esm1

Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.

AI-Powered Analysis

Machine-generated threat intelligence

AILast updated: 10/18/2026, 00:49:40 UTC

Technical Analysis

The aiohttp asynchronous HTTP client/server framework for Python has a vulnerability (CVE-2026-54275) affecting versions prior to 3.14.1. When an application makes multiple requests to the same domain but with different per-request server_hostname parameters, the TLS Server Name Indication (SNI) check can be bypassed if an existing TLS connection is reused. This means that the later requests may succeed without proper TLS hostname verification, potentially undermining TLS security guarantees. The vulnerability is resolved in aiohttp version 3.14.1.

Potential Impact

This vulnerability can lead to improper TLS hostname verification when reusing connections, which may allow an attacker to bypass TLS SNI checks. While the CVSS score is 7.5 (medium severity) with no confidentiality or integrity impact, it has a high impact on availability. There are no known exploits in the wild at this time.

Mitigation Recommendations

Upgrade aiohttp to version 3.14.1 or later, where this vulnerability is fixed. No other mitigations are indicated by the vendor advisory.

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Technical Details

Gcve Source
db.gcve.eu
Osv Id
UBUNTU-CVE-2026-54275
Osv Schema Version
1.7.0
Ecosystems
["Ubuntu:Pro:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:Pro:22.04:LTS","Ubuntu:Pro:24.04:LTS","Ubuntu:25.10","Ubuntu:26.10","Ubuntu:Pro:26.04:LTS"]
Cvss Version
3.1
State
PUBLISHED

Threat ID: 6ad3f5fd2cdf04f656663fec

Added to database: 10/17/2026, 22:26:05 UTC

Last enriched: 10/18/2026, 00:49:40 UTC

Last updated: 10/18/2026, 00:49:40 UTC

Views: 3

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