CVE-2025-46656 markdownify allows large headline prefixes such as <h9999999>, which causes memory consumption
An attacker can cause memory exhaustion and denial of service by providing large headline prefixes to the markdownify library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-46656?
CVE-2025-46656 is a low-severity denial of service vulnerability in python-markdownify, published on 26 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
python-markdownify (aka markdownify) before 0.14.1 allows large headline prefixes such as <h9999999> in addition to <h1> through <h6>. This causes memory consumption.
Weakness: CWE-1284
Which versions are affected by CVE-2025-46656?
3 open source packages ship an affected version, including markdownify. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
markdownify PyPI | All versions | 0.14.1 |
markdownify PyPI | All versions | 0.14.1 |
markdownify PyPI | All versions | 0.14.1 |
Products include Matthewwithanm Markdownify.
How do I fix CVE-2025-46656?
Upgrade markdownify to 0.14.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-46656 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-46656 exists.
Sources
Also known as GHSA-7mpr-5m44-h73r, PYSEC-2026-1604.