CVE catalog
CVE-2025-43859
h11 vulnerability
- Severity
- Critical · CVSS 9.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.59% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | python-h11 | sid | 0.16.0-2 | fixed |
| Debian | python-h11 | forky | 0.16.0-2 | fixed |
| Debian | python-h11 | trixie | 0.14.0-1.1 | fixed |
| Debian | python-h11 | bookworm | 0.14.0-1.1~deb12u1 | fixed |
| Ubuntu | python-h11 | noble | 0.14.0-1ubuntu0.24.04.1 | fixed |
| Ubuntu | python3-h11 | noble | 0.14.0-1ubuntu0.24.04.1 | fixed |
| PyPI | h11 | Not reported | 0.16.0 | fixed |
| PyPI | h11 | Not reported | 0.16.0 | fixed |
| Suse | python-h11 | linux micro 6.1 | 0.16.0-slfo.1.1_1.1 | fixed |
| Suse | python-httpcore | linux micro 6.1 | 0.16.3-slfo.1.1_2.1 | fixed |
| Suse | python-h11 | linux micro 6.0 | 0.16.0-1.1 | fixed |
| Suse | python-httpcore | linux micro 6.0 | 0.16.3-7.1 | fixed |
| Suse | python-h11 | linux enterprise module for python 3 15 sp6 | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise high performance computing 15 sp4-espos | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise high performance computing 15 sp4-ltss | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise high performance computing 15 sp5-espos | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise high performance computing 15 sp5-ltss | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise server 15 sp4-ltss | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise server 15 sp5-ltss | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise server for sap applications 15 sp4 | 0.14.0-150400.9.6.1 | fixed |
| Suse | python-h11 | linux enterprise server for sap applications 15 sp5 | 0.14.0-150400.9.6.1 | fixed |
| Opensuse | python-h11 | leap 15.6 | 0.14.0-150400.9.6.1 | fixed |
| Ubuntu | python-h11 | 24.04 | 0.14.0-1 | vulnerable |
| Ubuntu | python-h11 | 24.04 | 0.14.0-1ubuntu0.24.04.1 | fixed |
| Ubuntu | python-h11 | 24.04 | 0.14.0-1 | vulnerable |
| Ubuntu | python-h11 | 24.04 | 0.14.0-1ubuntu0.24.04.1 | fixed |
| Opensuse | python-h11 | tumbleweed | 0.16.0-1.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | python-h11 | source | sid | 0.14.0-1.1 | not yet assigned | Not reported | [1104056] |
| Debian | python-h11 | source | forky | 0.14.0-1.1 | not yet assigned | Not reported | [1104056] |
| Debian | python-h11 | source | trixie | 0.14.0-1.1 | not yet assigned | Not reported | [1104056] |
| Debian | python-h11 | source | bookworm | 0.14.0-1.1~deb12u1 | not yet assigned | Not reported | [1104056] |
| Ubuntu | python-h11 | deb | noble | 0.14.0-1ubuntu0.24.04.1 | Not reported | Not reported | Not reported |
| Ubuntu | python3-h11 | deb | noble | 0.14.0-1ubuntu0.24.04.1 | Not reported | Not reported | Not reported |
| PyPI | h11 | PyPI | Not reported | 0.16.0 | Not reported | GHSA-VQFR-H8MV-GHFJ | Not reported |
| PyPI | h11 | PyPI | Not reported | 0.16.0 | Not reported | PYSEC-2026-348 | Not reported |
| Suse | python-h11 | rpm | linux micro 6.1 | 0.16.0-slfo.1.1_1.1 | Not reported | SUSE-SU-2025:20330-1 | Not reported |
| Suse | python-httpcore | rpm | linux micro 6.1 | 0.16.3-slfo.1.1_2.1 | Not reported | SUSE-SU-2025:20330-1 | Not reported |
| Suse | python-h11 | rpm | linux micro 6.0 | 0.16.0-1.1 | Not reported | SUSE-SU-2025:20331-1 | Not reported |
| Suse | python-httpcore | rpm | linux micro 6.0 | 0.16.3-7.1 | Not reported | SUSE-SU-2025:20331-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise module for python 3 15 sp6 | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise high performance computing 15 sp4-espos | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise high performance computing 15 sp4-ltss | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise high performance computing 15 sp5-espos | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise high performance computing 15 sp5-ltss | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise server 15 sp4-ltss | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise server 15 sp5-ltss | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise server for sap applications 15 sp4 | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Suse | python-h11 | rpm | linux enterprise server for sap applications 15 sp5 | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Opensuse | python-h11 | rpm | leap 15.6 | 0.14.0-150400.9.6.1 | Not reported | SUSE-SU-2025:1430-1 | Not reported |
| Ubuntu | python-h11 | deb | 24.04 | 0.14.0-1ubuntu0.24.04.1 | Not reported | USN-7503-1 | Not reported |
| Ubuntu | python-h11 | deb | 24.04 | 0.14.0-1ubuntu0.24.04.1 | Not reported | UBUNTU-CVE-2025-43859 | Not reported |
| Opensuse | python-h11 | rpm | tumbleweed | 0.16.0-1.1 | Not reported | OPENSUSE-SU-2025:15032-1 | Not reported |
OpenFactory catalog packages
[openSUSE Tumbleweed]
- [python313-h11]Unknown
Source package: [python-h11]
Details (1)
0.16.0-1.4· noarch · tumbleweedUnknown · Fixed:
0.16.0-1.1Version impact unknown
usn · python-h11 · opensuse · tumbleweed
- [python314-h11]Unknown
Source package: [python-h11]
Details (1)
0.16.0-1.4· noarch · tumbleweedUnknown · Fixed:
0.16.0-1.1Version impact unknown
usn · python-h11 · opensuse · tumbleweed
[Debian 12 (Bookworm)]
- [python3-h11]Fixed
Source package: [python-h11]
Details (2)
0.14.0-1.1~deb12u1· all · bookwormFixed · Fixed:
0.14.0-1.1~deb12u1usn · python-h11 · debian · bookworm; usn · python-h11 · debian · 12
0.14.0-1.1~deb12u1· all · bookwormFixed · Fixed:
0.14.0-1.1~deb12u1usn · python-h11 · debian · bookworm; usn · python-h11 · debian · 12
[Debian 13 (Trixie)]
- [python3-h11]Fixed
Source package: [python-h11]
Details (2)
0.14.0-1.1· all · trixieFixed · Fixed:
0.14.0-1.1usn · python-h11 · debian · 13
0.14.0-1.1· all · trixieFixed · Fixed:
0.14.0-1.1usn · python-h11 · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/suse-su-2025_1430-1.json]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2025-43859]
- [https://osv.dev/vulnerability/GHSA-vqfr-h8mv-ghfj]
- [https://osv.dev/vulnerability/SUSE-SU-2025:1430-1]
- [https://osv.dev/vulnerability/SUSE-SU-2025:20330-1]
- [https://osv.dev/vulnerability/SUSE-SU-2025:20331-1]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2025-43859]
- [https://osv.dev/vulnerability/USN-7503-1]
- [https://osv.dev/vulnerability/openSUSE-SU-2025:15032-1]
- [https://security-tracker.debian.org/tracker/CVE-2025-43859]
- [https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-43859.json]
- [https://ubuntu.com/security/notices/USN-7503-1]
- [https://wid.cert-bund.de/.well-known/csaf/white/2025/wid-sec-w-2025-1022.json]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]