CVE-2025-43859
Apache h11 Chunked-Coding Request Smuggling Vulnerability
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.
INFO
Published Date :
April 24, 2025, 7:15 p.m.
Last Modified :
April 29, 2025, 1:52 p.m.
Source :
[email protected]
Remotely Exploitable :
Yes !
Impact Score :
5.2
Exploitability Score :
3.9
Public PoC/Exploit Available at Github
CVE-2025-43859 has a 1 public PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
Affected Products
The following products are affected by CVE-2025-43859
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-43859.
| URL | Resource |
|---|---|
| https://github.com/python-hyper/h11/commit/114803a29ce50116dc47951c690ad4892b1a36ed | |
| https://github.com/python-hyper/h11/security/advisories/GHSA-vqfr-h8mv-ghfj |
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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Python Jupyter Notebook
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-43859 vulnerability anywhere in the article.
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Daily CyberSecurity
CVE-2025-43859: Request Smuggling Vulnerability in Python’s h11 HTTP Library
A critical vulnerability tracked as CVE-2025-43859 has been disclosed in h11, a minimalist, I/O-agnostic HTTP/1.1 protocol library written in Python. Rated CVSS 9.1, the flaw could enable request smug ... Read more
The following table lists the changes that have been made to the
CVE-2025-43859 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Apr. 24, 2025
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Added CWE CWE-444 Added Reference https://github.com/python-hyper/h11/commit/114803a29ce50116dc47951c690ad4892b1a36ed Added Reference https://github.com/python-hyper/h11/security/advisories/GHSA-vqfr-h8mv-ghfj
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-43859 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-43859
weaknesses.