CVE-2025-69534: in Python-Markdown
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 Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
pip/Markdownto a version that resolves this vulnerability.Fixed in 3.8.1 - Upgrade
Upgrade
debian/pypy3to a version that resolves this vulnerability.Fixed in 8.0.0+dfsg-1 - Upgrade
Upgrade
debian/python3.11to a version that resolves this vulnerability.Fixed in 3.11.2-6+deb12u9 - Upgrade
Upgrade
debian/python3.13to a version that resolves this vulnerability.Fixed in 3.13.4-1 - Upgrade
Upgrade
debian/pypy3to a version that resolves this vulnerability.Fixed in 8.0.1+dfsg-1 - Upgrade
Upgrade
debian/python3.13to a version that resolves this vulnerability.Fixed in 3.13.5-2+deb13u5Fixed in 3.13.18-1 - Upgrade
Upgrade
debian/python3.14to a version that resolves this vulnerability.Fixed in 3.14.10-1 - Upgrade
Upgrade
Python-Markdownto a version that resolves this vulnerability.Fixed in 3.8.1
Event History
Frequently Asked Questions
What is the severity of CVE-2025-69534?
CVE-2025-69534 has been identified as a critical vulnerability due to the potential for triggering an unhandled AssertionError, which can lead to application crashes.
How do I fix CVE-2025-69534?
To mitigate CVE-2025-69534, upgrade Python-Markdown to version 3.8.1 or later.
What causes CVE-2025-69534?
CVE-2025-69534 is caused by malformed HTML-like sequences that the html.parser.HTMLParser cannot handle properly.
Which versions of Python-Markdown are affected by CVE-2025-69534?
CVE-2025-69534 affects Python-Markdown version 3.8 specifically.
What impact does CVE-2025-69534 have on applications?
Applications that utilize Python-Markdown for parsing malformed markdown could experience crashes due to unhandled exceptions.