CVE-2025-69534

NameCVE-2025-69534
DescriptionPython-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.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
pypy3 (PTS)bullseye7.3.5+dfsg-2+deb11u2vulnerable
bullseye (security)7.3.5+dfsg-2+deb11u5vulnerable
bookworm7.3.11+dfsg-2+deb12u3vulnerable
trixie7.3.19+dfsg-2vulnerable
sid, forky7.3.20+dfsg-4vulnerable
python2.7 (PTS)bullseye2.7.18-8+deb11u1vulnerable
python3.11 (PTS)bookworm3.11.2-6+deb12u6vulnerable
bookworm (security)3.11.2-6+deb12u3vulnerable
python3.13 (PTS)trixie3.13.5-2fixed
sid, forky3.13.12-1fixed
python3.14 (PTS)sid, forky3.14.3-1fixed
python3.9 (PTS)bullseye3.9.2-1vulnerable
bullseye (security)3.9.2-1+deb11u5vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
jython2.7source(unstable)(unfixed)
pypy3source(unstable)(unfixed)
python2.7source(unstable)(unfixed)
python3.11source(unstable)(unfixed)
python3.13source(unstable)3.13.4-1
python3.14source(unstable)(not affected)
python3.9source(unstable)(unfixed)

Notes

- python3.14 <not-affected> (Fixed before initial upload to Debian unstable)
While reported against python-markdown, the actual issue in in Python itself
https://github.com/Python-Markdown/markdown/issues/1534
https://github.com/python/cpython/issues/77057
https://github.com/python/cpython/commit/76c0b01bc401c3e976011bbc69cec56dbebe0ad5 (v3.15.0a1)
https://github.com/python/cpython/commit/381159b2beabbd6b3c0babe4d7ba7fbdeb23ce06 (v3.14.0b2)
https://github.com/python/cpython/commit/aa0c3d1098e7fdcc74b753aadf18dd07ddbc76b0 (v3.13.4)

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