CVE-2025-53643: aiohttp Request Smuggling — Fix

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.12.14, the Python parser is vulnerable to a request smuggling vulnerability due to not parsing trailer sections of an HTTP request. If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections. Version 3.12.14 contains a patch for this issue.

Is your site exposed to CVE-2025-53643?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Weakness Type (CWE)

CWE-444 CWE-444

Affected Products

Vendor	Product	Versions
aiohttp	aiohttp	< 3.12.14

References

Advisories & Patches

https://github.com/aio-libs/aiohttp/commit/e8d774f635dc6d1cd3174d0e38891da5de0e2b6a https://github.com/aio-libs/aiohttp/security/advisories/GHSA-9548-qrrj-x5pj

Frequently Asked Questions

What is CVE-2025-53643? +

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.12.14, the Python parser is vulnerable to a request smuggling vulnerability due to not parsing trailer sections of an HTTP request. If a pure Python version of aiohttp is installed (i.e. without the usual C extensions) or AIOHTTP_NO_EXTENSIONS is enabled, then an attacker may be able to execute a request smuggling attack to bypass certain firewalls or proxy protections. Version 3.12.14 contains a patch for this issue. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2025-53643? +

CVE-2025-53643 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-53643? +

CVE-2025-53643 affects products from aiohttp, specifically: aiohttp. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-53643? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-59249

Inconsistent interpretation of HTTP requests (HTTP response smuggling) vulnerability in elixir-mint mint allows a malicious HTTP/1 server to desynchronize a …

CVE-2026-50197

Skipper is an HTTP router and reverse proxy for service composition. Prior to 0.26.10, zalando/skipper's OpenPolicyAgent integration silently bypasses request-body …

CVE-2026-6338

A HTTP request smuggling and desynchronization vulnerability affects Kong Gateway Enterprise 3.4, 3.10, 3.11, 3.12, 3.13, and 3.14 series. The …

CVE-2026-39805

Inconsistent Interpretation of HTTP Requests vulnerability in mtrudel bandit allows HTTP request smuggling via duplicate Content-Length headers. 'Elixir.Bandit.Headers':get_content_length/1 in lib/bandit/headers.ex …

CVE-2026-50052

In Vinyl Cache before 9.0.1 and Varnish Cache before 9.0.3, a deficiency in HTTP/2 request parsing can be exploited to …

CVE-2026-59898

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, ab attacker can force WebSocket upgrade …

CVE-2025-53643