SecuriTricks - CVE-2025-43859

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.

Product(s) Impacted

Vendor	Product	Versions
H11	H11	<0.16.0

Weaknesses

Common security weaknesses mapped to this vulnerability.

CWE-444

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

*CPE(s)

Affected systems and software identified for this CVE.

Type	Vendor	Product	Version	Update	Edition	Language	Software Edition	Target Software	Target Hardware	Other Information
a	h11	h11	<0.16.0	/	/	/	/	/	/	/

References

https://github.com/python-hyper/h11/commit/114803a29ce50116dc47951c690ad4892b1a36ed

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

CVSS Score

9.1 / 10

CVSS Data - 3.1

Attack Vector: NETWORK
Attack Complexity: LOW
Privileges Required: NONE
Scope: UNCHANGED
Confidentiality Impact: HIGH
Integrity Impact: HIGH
Availability Impact: NONE

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

View Vector String

Timeline

Published: April 24, 2025, 7:15 p.m.
Last Modified: April 24, 2025, 7:15 p.m.

Status : Received

CVE has been recently published to the CVE List and has been received by the NVD.

More info

Source

security-advisories@github.com

CVE-2025-43859