CVE-2025-43859

critical · 9.1

h11 is a Python implementation of HTTP/1.1. Prior to version 0.16.0, a leniency in h11's parsing of line terminators in chunked-coding message bodies can lead to request smuggling vulnerabilities under certain conditions. This issue has been patched in version 0.16.0. Since exploitation requires the combination of buggy h11 with a buggy (reverse) proxy, fixing either component is sufficient to mitigate this issue.

9.1

CVSS

0.6%

EPSS (exploit prob.)

46th

EPSS percentile

2025-04-24

Published

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

Weaknesses

CWE-444

References

https://github.com/python-hyper/h11/commit/114803a29ce50116dc47951c690ad4892b1a36ed
https://github.com/python-hyper/h11/security/advisories/GHSA-vqfr-h8mv-ghfj

Query this programmatically:

curl https://evil-db.io/api/v1/cve/CVE-2025-43859