CVE-2026-54275 AIOHTTP: TLS Server Hostname Override Is Ignored When Reusing HTTPS Connections
Attackers can bypass TLS hostname verification in aiohttp by reusing connections, potentially enabling man-in-the-middle attacks against applications using the library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-54275?
CVE-2026-54275 is a low-severity vulnerability in aio-libs aiohttp, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, the server_hostname 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 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. This vulnerability is fixed in 3.14.1.
Weakness: CWE-297
Which versions are affected by CVE-2026-54275?
3 open source packages ship an affected version, including aiohttp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
aiohttp PyPI | All versions | 3.14.1 |
aiohttp PyPI | All versions | 3.14.1 |
aiohttp PyPI | All versions | 3.14.1 |
Products include Aiohttp Aiohttp.
How do I fix CVE-2026-54275?
Upgrade aiohttp to 3.14.1 or later.
Is CVE-2026-54275 being exploited?
There is no known exploitation of CVE-2026-54275 in the wild and no public exploit code.
Other vulnerabilities in aio-libs aiohttp
- CVE-2024-52303 aiohttp memory leak when middleware is enabled when requesting a resource with a non-allowed method
- CVE-2025-69223 AIOHTTP's HTTP Parser auto_decompress feature is vulnerable to zip bomb
- CVE-2024-30251 Denial of service when trying to parse malformed POST requests in aiohttp
- CVE-2023-49081 aiohttp's ClientSession is vulnerable to CRLF injection via version
- CVE-2026-22815 AIOHTTP: Uncapped memory usage possible through aiohttp allowing unlimited trailer headers
Sources
Also known as CLEANSTART-2026-QD31009, CLEANSTART-2026-YI50713, DEBIAN-CVE-2026-54275, ECHO-3b67-4bd3-d8be, GHSA-4m7w-qmgq-4wj5, MINI-4m8q-c56p-c9hh and 19 more.