CVE-2025-43859 — h11 accepts some malformed Chunked-Encoding bodies
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 smuggli…
Published: 2025-04-24 · CVSS: 9.1 · CVSS 3.1
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7