Description
Python-Markdown version 3.8 contain a vulnerability where malformed HTML-like sequences can cause html.parser.HTMLParser to raise an unhandled AssertionError during Markdown parsing. Because Python-Markdown does not catch this exception, any application that processes attacker-controlled Markdown may crash. This enables remote, unauthenticated Denial of Service in web applications, documentation systems, CI/CD pipelines, and any service that renders untrusted Markdown. The issue was acknowledged by the vendor and fixed in version 3.8.1. This issue causes a remote Denial of Service in any application parsing untrusted Markdown, and can lead to Information Disclosure through uncaught exceptions.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | pypy3 | 8.0.0+dfsg-1 | — |
| Debian 13 | pypy3 | No fix yet | — |
| Debian 13 | python3.13 | 3.13.4-1 | — |
| Debian 12 | pypy3 | No fix yet | — |
| Debian 12 | python3.11 | 3.11.2-6+deb12u9 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | pypy3 | No fix yet | — |
| Ubuntu 26.04 LTS | pypy3 | No fix yet | — |
| Ubuntu 26.04 LTS | python3.14 | 3.14.4-1ubuntu0.1 | USN-8509-1 |
| Ubuntu 25.10 | pypy3 | No fix yet | — |
| Ubuntu 24.04 LTS | pypy3 | No fix yet | — |
| Ubuntu 24.04 LTS | python3.12 | 3.12.3-1ubuntu0.15 | USN-8509-1 |
| Ubuntu 22.04 LTS | pypy3 | No fix yet | — |
| Ubuntu 22.04 LTS | python3.10 | 3.10.12-1~22.04.16 | USN-8509-1 |
Show 6 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | pypy3 | No fix yet | — |
| Ubuntu Pro 22.04 LTS | python2.7 +1 | No fix yet | — |
| Ubuntu Pro 20.04 LTS | python2.7 +2 | No fix yet | — |
| Ubuntu Pro 18.04 LTS | python2.7 +3 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | python2.7 | 2.7.12-1ubuntu0~16.04.18+esm21 | USN-8614-1 |
| Ubuntu Pro 16.04 LTS | python3.5 | 3.5.2-2ubuntu0~16.04.13+esm24 | USN-8614-1 |
| Ubuntu Pro 14.04 LTS | python2.7 +2 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | python-markdown +1 | 3.5.1-6.el10_2.1 | RHSA-2026:19155 |
| RHEL 9 | python-markdown +1 | 3.3.4-4.el9_8.2 | RHSA-2026:19366 |
Show 8 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Satellite Capsule 6 | python-markdown +1 | 3.8.2-1.el8pc | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite Capsule 6 | python-pillow +1 | 12.1.1-1.el8pc | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite Capsule 6 | python-pyOpenSSL +1 | 24.1.0-2.el8pc | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite Capsule 6 | python3.12-django | 4.2.30-1.el9pc | RHSA-2026:14835 |
| Red Hat Satellite Capsule 6 | python3.12-markdown | 3.8.2-1.el9pc | RHSA-2026:14835 |
| Red Hat Satellite Capsule 6 | python3.12-pyOpenSSL | 26.0.0-2.el9pc | RHSA-2026:14835 |
| Red Hat Satellite Capsule 6 | rubygem-activesupport | 6.1.7.8-2.el8sat | RHSA-2026:14874, RHSA-2026:14873, RHSA-2026:14835 |
| Red Hat Satellite 6 | candlepin +1 | 4.4.25-1.el8sat | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite 6 | python-markdown +1 | 3.8.2-1.el8pc | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite 6 | python-pillow +1 | 12.1.1-1.el8pc | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite 6 | python-pyOpenSSL +1 | 24.1.0-2.el8pc | RHSA-2026:14874, RHSA-2026:14873 |
| Red Hat Satellite 6 | python3.12-django | 4.2.30-1.el9pc | RHSA-2026:14835 |
| Red Hat Satellite 6 | python3.12-markdown | 3.8.2-1.el9pc | RHSA-2026:14835 |
| Red Hat Satellite 6 | python3.12-pyOpenSSL | 26.0.0-2.el9pc | RHSA-2026:14835 |
| Red Hat Satellite 6 | rubygem-activesupport | 6.1.7.8-2.el8sat | RHSA-2026:14874, RHSA-2026:14873, RHSA-2026:14835 |
| RHEL 10.0 EUS | python-markdown +1 | 3.5.1-6.el10_0.1 | RHSA-2026:20677 |
| RHEL 9.6 EUS | python-markdown +1 | 3.3.4-4.el9_6.2 | RHSA-2026:20676 |
| RHEL 9.4 EUS | python-markdown +1 | 3.3.4-4.el9_4.2 | RHSA-2026:20674 |
| Red Hat Ansible Automation Platform Inside 2 | receptor | 1.6.4-2.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform Inside 2 | receptorctl | 1.6.4-2.el9ap | RHSA-2026:13508 |
| Red Hat Ansible Automation Platform Developer 2 | automation-controller +1 | 4.7.11-2.el9ap | RHSA-2026:13508 |
| Red Hat Ansible Automation Platform Developer 2 | receptor | 1.6.4-2.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform Developer 2 | receptorctl | 1.6.4-2.el9ap | RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | automation-controller +3 | 4.7.11-2.el9ap | RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | automation-controller-venv-tower | 4.6.28-3.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | automation-gateway-proxy +1 | 2.5.10-5.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | automation-gateway-server +11 | 2.5.20260422-2.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | automation-platform-ui | 2.6.8-1.el9ap | RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | python3.12-django-ansible-base+resource_registry | 2.6.20260422-1.el9ap | RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | python3.12-jwcrypto | 1.5.7-1.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | python3.12-markdown | 3.10.2-1.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | python3.12-pyOpenSSL | 26.0.0-1.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | python3.12-pyasn1 | 0.6.3-1.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | python3.12-pyjwt +1 | 2.12.1-1.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | receptor | 1.6.4-2.el8ap | RHSA-2026:13512, RHSA-2026:13508 |
| Red Hat Ansible Automation Platform 2 | receptorctl | 1.6.4-2.el9ap | RHSA-2026:13508 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | python3-markdown | 3.5.1-6.el10_2.1 | ALSA-2026:19155 |
| AlmaLinux 9 | python3-markdown | 3.3.4-4.el9_8.2 | ALSA-2026:19366 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | python-markdown | 3.5.1-6.el10_2.1 | RLSA-2026:19155 |
| Rocky Linux 9 | python-markdown | 3.3.4-4.el9_8.2 | RLSA-2026:19366 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 15.6 | python-Markdown | 3.5.2-150600.3.3.1 | SUSE-SU-2026:0846-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | python3-markdown | 3.3.4-2.amzn2023.0.4 | ALAS2023-2026-1492 |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | python3-markdown | 3.5.1-6.el10_2.1 | ELSA-2026-19155 |
| Oracle Linux 9 | python3-markdown | 3.3.4-4.el9_8.2 | ELSA-2026-19366 |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | superset-6.0 | 6.0.0-r4 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | markdown | < 3.8.1 | 3.8.1 | GHSA-5wmx-573v-2qwq |
| PyPI | markdown | <= 3.8 | — | PYSEC-2026-89 |
Advisories 23
- SSA-457936 SSA-457936: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP V3.1.7 Siemens ProductCERT · Nov 10, 2026
- ALSA-2026:19366 Important: python-markdown security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:19155 Important: python-markdown security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:14873 Red Hat Security Advisory: Satellite 6.17.8 Async Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:14874 Red Hat Security Advisory: Satellite 6.16.8 Async Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:13512 Red Hat Security Advisory: Red Hat Ansible Automation Platform 2.5 Product Security and Bug Fix Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:13508 Red Hat Security Advisory: Red Hat Ansible Automation Platform 2.6 Product Security and Bug Fix Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:20677 Red Hat Security Advisory: python-markdown security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:20674 Red Hat Security Advisory: python-markdown security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:20676 Red Hat Security Advisory: python-markdown security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:19366 Red Hat Security Advisory: python-markdown security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:19155 Red Hat Security Advisory: python-markdown security update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- RHSA-2026:14835 Red Hat Security Advisory: Satellite 6.18.5 Async Update Red Hat Security Advisories (RHSA) · Oct 10, 2026
- WID-SEC-2026-1610 Red Hat Enterprise Linux (JWCrypto und python-markdown): Mehrere Schwachstellen ermöglichen Denial of Service BSI CERT-Bund (WID) · Oct 7, 2026
- VDE-2026-088 METTLER TOLEDO: LabX Standard and Enterprise Report on External Component Analysis - v21.4 CERT@VDE · Sep 10, 2026
- USN-8614-1 python2.7, python3.5 vulnerabilities Ubuntu Security Notices (USN) · Jul 28, 2026
- ELSA-2026-19155 Important: python-markdown security update (Oracle Linux 10) Oracle Linux Security Advisories (ELSA) · Jul 16, 2026
- USN-8509-1 python3.10, python3.12, python3.14 vulnerabilities Ubuntu Security Notices (USN) · Jul 6, 2026
- ELSA-2026-19366 Important: python-markdown security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Jun 23, 2026
- RLSA-2026:19155 Important: python-markdown security update Rocky Linux Security Advisories · May 29, 2026
- RLSA-2026:19366 Important: python-markdown security update Rocky Linux Security Advisories · May 28, 2026
- ALAS2023-2026-1492 Important: python-markdown security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Mar 27, 2026
- SUSE-SU-2026:0846-1 Security update for python-Markdown SUSE / openSUSE Security Updates · Mar 23, 2026