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Not in CISA KEV
HIGH severity

Python-Markdown has an Uncaught ExceptionGHSA-5wmx-573v-2qwq

HIGHFix: Python-Markdown/markdown#1535

GHSA-5wmx-573v-2qwq is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in markdown. A fix is available for markdown — see the affected versions and patch details below.

Also known asCVE-2025-69534PYSEC-2026-89
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for GHSA-5wmx-573v-2qwq.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs52th percentile — riskier than 52% of all scored CVEsHighest risk
0.00%0.39%0.78%1.16%0.4%0.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐍markdown

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPImarkdownall versions3.8.1pip install --upgrade 'markdown==3.8.1'

Affected Products

1 product · 1 configurations
Application
markdownpython-markdown
1 version
3.8

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for markdown, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update markdown to 3.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5wmx-573v-2qwq is resolved across your whole dependency graph.

  3. Workarounds

    Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

To exploit this flaw, an attacker must be able to supply a specially crafted payload to be processed by an application using Python-Markdown. Additionally, the security impact of this vulnerability is limited to an information disclosure via the unhandled exception stack trace and a denial of service. There is no…

Workaround published by Red Hat
To mitigate this vulnerability, wrap your markdown parsing function in a try/except block. This catches the unhandled exception, preventing both the application crash and the stack trace leak.
Source: Red Hat security advisory for GHSA-5wmx-573v-2qwq (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Ansible Automation Platform 2.5 for RHEL 8python3.12-markdown-0:3.10.2-1.el8apRHSA-2026:13512
Red Hat Ansible Automation Platform 2.6 for RHEL 9automation-controller-0:4.7.11-2.el9apRHSA-2026:13508
Red Hat Enterprise Linux 10python-markdown-0:3.5.1-6.el10_2.1RHSA-2026:19155
Red Hat Enterprise Linux 10.0 Extended Update Supportpython-markdown-0:3.5.1-6.el10_0.1RHSA-2026:20677
Red Hat Enterprise Linux 9python-markdown-0:3.3.4-4.el9_8.2RHSA-2026:19366
Red Hat Enterprise Linux 9.4 Extended Update Supportpython-markdown-0:3.3.4-4.el9_4.2RHSA-2026:20674
Red Hat Enterprise Linux 9.6 Extended Update Supportpython-markdown-0:3.3.4-4.el9_6.2RHSA-2026:20676
Red Hat Satellite 6.16 for RHEL 8python-markdown-0:3.8.2-1.el8pcRHSA-2026:14874

Frequently Asked Questions

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 appli
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Python-Markdown has an Uncaught Exception (High 7.5)