CVE-2026-54275: AIOHTTP: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections

Published Jun 15, 2026
·
Updated

Summary

The serverhostname 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 serverhostname 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 keepalive if you need to change the serverhostname check between requests.

-----

Patch: https://github.com/aio-libs/aiohttp/commit/0ca2b6c28a25726527a8b60f25960262a91ed0e0

Other sources

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, the serverhostname TLS SNI check can be bypassed when an existing connection is reused. If an application makes multiple requests to the same domain, but with different per-request serverhostname parameters, then the later calls may succeed by reusing the existing connection when they should have been rejected due to the TLS SNI check. This vulnerability is fixed in 3.14.1.

— MITRE

Affected Software

2 affected componentsFixes available
pip/aiohttp<=3.14.0
3.14.1
aiohttp aiohttp<3.14.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade pip/aiohttp to a version that resolves this vulnerability.

    Fixed in 3.14.1
  2. Upgrade

    Upgrade aio-libs/aiohttp to a version that resolves this vulnerability.

    Fixed in 3.14.1
  3. Configuration

    Disable keep_alive if you need to change the per-request `server_hostname` check between requests; if keep_alive is enabled, later requests may reuse an existing HTTPS connection and bypass the TLS SNI (`server_hostname`) check.

    AIOHTTP keep_alive = disable (disable keep_alive)

Event History

Jun 15, 2026
Advisory Published
via GitHub·08:11 PM
Data Sourced
via GitHub·08:11 PM
DescriptionWeaknessAffected Software
Jun 22, 2026
CVE Published
via MITRE·04:34 PM
Data Sourced
via MITRE·04:34 PM
DescriptionWeakness
Data Sourced
via NVD·06:16 PM
DescriptionSeverityWeaknessAffected Software
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Frequently Asked Questions

1

What is the severity of CVE-2026-54275?

CVE-2026-54275 has a low severity rating of 2.7.

2

What does CVE-2026-54275 affect?

CVE-2026-54275 affects the AIOHTTP library when reusing HTTPS connections.

3

What is the main issue described in CVE-2026-54275?

The main issue is that the TLS Server Hostname Override can be ignored when an existing connection is reused.

4

How does CVE-2026-54275 impact application security?

CVE-2026-54275 can allow later requests to succeed even with different server_hostname parameters, which may lead to unexpected behavior.

5

How do I mitigate CVE-2026-54275?

To mitigate CVE-2026-54275, consider avoiding the reuse of HTTPS connections when using different server_hostname parameters.

Company

Resources

Contact

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CVE-2026-54275 - AIOHTTP: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections - SecAlerts