AUGUST 4, 2026
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Case File

CVE-2025-43859

CRITICAL · CVSS 9.1 EPSS 0.58% Public Exploit

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2025-04-24 · Last synced 2026-08-04

CyberRota Analysis

This is a critical severity vulnerability with a CVSS score of 9.1. Public exploit code or proof-of-concept references have been detected in its references.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

Detected Signals
exploit

Note: these links are listed for security research and verification purposes only.

CVE
CVE-2025-43859
Severity
CRITICAL
CVSS
9.1
EPSS
0.58%

Original NVD Description

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.