CVE-2025-53643
Request Smuggling vulnerability in aiohttp (PyPI)
What is CVE-2025-53643 About?
The Python parser in `aiohttp` is vulnerable to request smuggling if running a pure Python version without C extensions. This flaw arises from not parsing trailer sections of an HTTP request, allowing attackers to bypass firewalls or proxies. Exploitation is possible when specific AIOHTTP configurations are present.
Affected Software
Technical Details
This vulnerability is a request smuggling flaw in the pure Python implementation of aiohttp's HTTP parser. It occurs when a pure Python version of aiohttp is installed (i.e., without its usual C extensions) or if the AIOHTTP_NO_EXTENSIONS environment variable is enabled. The core issue is that the parser fails to correctly interpret or process trailer sections of an HTTP request. This parsing discrepancy between aiohttp and upstream proxies or firewalls creates an opportunity for request smuggling. An attacker can craft HTTP requests that are interpreted differently by an intermediate proxy/firewall and the aiohttp server, allowing them to 'smuggle' a second, unauthorized request within the first. This can bypass security controls, firewalls, or proxy protections that rely on a consistent interpretation of HTTP requests.
What is the Impact of CVE-2025-53643?
Successful exploitation may allow attackers to bypass security firewalls or proxy protections, access restricted resources, and perform unauthorized actions.
What is the Exploitability of CVE-2025-53643?
Exploitation of this vulnerability requires specific environmental conditions: either a pure Python version of aiohttp must be installed (without C extensions), or the AIOHTTP_NO_EXTENSIONS flag must be enabled. No authentication or special privileges are required for the attacker to send crafted requests. This is a remote attack that targets the HTTP parsing logic. The complexity is moderate, as it involves crafting HTTP requests that exploit the parsing discrepancies between front-end proxies/firewalls and the aiohttp backend. Special conditions include the presence of proxies or firewalls that can be tricked by the smuggling technique. The risk is heightened in environments where aiohttp is deployed with non-default configurations that disable C extensions.
What are the Known Public Exploits?
| PoC Author | Link | Commentary |
|---|---|---|
| No known exploits | ||
What are the Available Fixes for CVE-2025-53643?
About the Fix from Resolved Security
Available Upgrade Options
- aiohttp
- <3.12.14 → Upgrade to 3.12.14
Struggling with dependency upgrades?
See how Resolved Security's drop-in replacements make it simple.
Book a demoAdditional Resources
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-9548-qrrj-x5pj
- https://github.com/aio-libs/aiohttp/commit/e8d774f635dc6d1cd3174d0e38891da5de0e2b6a
- https://github.com/aio-libs/aiohttp/security/advisories/GHSA-9548-qrrj-x5pj
- https://github.com/aio-libs/aiohttp/commit/e8d774f635dc6d1cd3174d0e38891da5de0e2b6a
- https://nvd.nist.gov/vuln/detail/CVE-2025-53643
- https://github.com/aio-libs/aiohttp
- https://osv.dev/vulnerability/GHSA-9548-qrrj-x5pj
What are Similar Vulnerabilities to CVE-2025-53643?
Similar Vulnerabilities: CVE-2023-44487 , CVE-2023-38035 , CVE-2020-1934 , CVE-2021-33107 , CVE-2023-4928
