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.
Published: 2025-04-24
Score: 9.1 Critical
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
EUVD EUVD EUVD-2025-11981 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.
Github GHSA Github GHSA GHSA-vqfr-h8mv-ghfj h11 accepts some malformed Chunked-Encoding bodies
Ubuntu USN Ubuntu USN USN-7503-1 h11 vulnerability
History

Fri, 06 Jun 2025 22:00:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:ansible_automation_platform:2.4::el8

Wed, 28 May 2025 14:15:00 +0000

Type Values Removed Values Added
First Time appeared Redhat ansible Automation Platform
CPEs cpe:/a:redhat:ansible_automation_platform:2.5::el8
cpe:/a:redhat:ansible_automation_platform:2.5::el9
Vendors & Products Redhat ansible Automation Platform

Wed, 14 May 2025 15:00:00 +0000

Type Values Removed Values Added
First Time appeared Redhat
Redhat openstack
CPEs cpe:/a:redhat:openstack:17.1::el9
cpe:/a:redhat:openstack:18.0::el9
Vendors & Products Redhat
Redhat openstack

Tue, 29 Apr 2025 03:30:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Important


Thu, 24 Apr 2025 19:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 24 Apr 2025 18:30:00 +0000

Type Values Removed Values 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.
Title h11 accepts some malformed Chunked-Encoding bodies
Weaknesses CWE-444
References
Metrics cvssV3_1

{'score': 9.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N'}


Subscriptions

Redhat Ansible Automation Platform Openstack
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2025-04-24T19:02:45.130Z

Reserved: 2025-04-17T20:07:08.556Z

Link: CVE-2025-43859

cve-icon Vulnrichment

Updated: 2025-04-24T19:02:18.751Z

cve-icon NVD

Status : Deferred

Published: 2025-04-24T19:15:47.060

Modified: 2026-04-15T00:35:42.020

Link: CVE-2025-43859

cve-icon Redhat

Severity : Important

Publid Date: 2025-04-24T18:15:53Z

Links: CVE-2025-43859 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses