CVE-2025-69534 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.
Python-Markdown has an Uncaught Exception
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 CVE-2025-69534.
EPSS Exploitation Probability
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
markdownReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | markdown | all versions | 3.8.1pip install --upgrade 'markdown==3.8.1' |
Affected Products
markdownpython-markdownDetection & mitigation playbook
Open-source dependencyDetect
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.
Fix
Update markdown to 3.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-69534 is resolved across your whole dependency graph.
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.
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…
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 CVE-2025-69534 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Ansible Automation Platform 2.5 for RHEL 8 | python3.12-markdown-0:3.10.2-1.el8ap | RHSA-2026:13512 |
| Red Hat Ansible Automation Platform 2.6 for RHEL 9 | automation-controller-0:4.7.11-2.el9ap | RHSA-2026:13508 |
| Red Hat Enterprise Linux 10 | python-markdown-0:3.5.1-6.el10_2.1 | RHSA-2026:19155 |
| Red Hat Enterprise Linux 10.0 Extended Update Support | python-markdown-0:3.5.1-6.el10_0.1 | RHSA-2026:20677 |
| Red Hat Enterprise Linux 9 | python-markdown-0:3.3.4-4.el9_8.2 | RHSA-2026:19366 |
| Red Hat Enterprise Linux 9.4 Extended Update Support | python-markdown-0:3.3.4-4.el9_4.2 | RHSA-2026:20674 |
| Red Hat Enterprise Linux 9.6 Extended Update Support | python-markdown-0:3.3.4-4.el9_6.2 | RHSA-2026:20676 |
| Red Hat Satellite 6.16 for RHEL 8 | python-markdown-0:3.8.2-1.el8pc | RHSA-2026:14874 |
Frequently Asked Questions
Is CVE-2025-69534 in your dependencies?
Find it across PyPI, including transitive dependencies.