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PYSEC-2026-1099

LowCVSS 2.7 / 10
Published Jul 7, 2026·Last modified Jul 7, 2026
Affected Components(1)
PyPI logoaiohttp
< 3.13.3
Description

Summary

The Python HTTP parser may allow a request smuggling attack with the presence of non-ASCII characters.

Impact

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.


Patch: https://github.com/aio-libs/aiohttp/commit/32677f2adfd907420c078dda6b79225c6f4ebce0

Risk Scores
Base Score
2.7

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.

Threat Intelligence
2.7

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.21%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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