CVE-2025-69534
Python-Markdown HTML Injection Denial of Service
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.
INFO
Published Date :
March 5, 2026, 3:16 p.m.
Last Modified :
March 13, 2026, 1:25 a.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update Python-Markdown to version 3.8.1.
- Ensure Markdown parsing exceptions are handled.
- Avoid parsing untrusted Markdown content.
- Monitor application logs for parsing errors.
Public PoC/Exploit Available at Github
CVE-2025-69534 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-69534.
| URL | Resource |
|---|---|
| https://github.com/Python-Markdown/markdown | Product |
| https://github.com/Python-Markdown/markdown/actions/runs/15736122892 | Product |
| https://github.com/Python-Markdown/markdown/issues/1534 | Exploit Issue Tracking |
| http://www.openwall.com/lists/oss-security/2026/03/06/4 | Mailing List Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-69534 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-69534
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
Python Dockerfile Shell JavaScript HTML CSS
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-69534 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-69534 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Mar. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:python-markdown:markdown:3.8:*:*:*:*:python:*:* Added Reference Type CVE: http://www.openwall.com/lists/oss-security/2026/03/06/4 Types: Mailing List, Third Party Advisory Added Reference Type MITRE: https://github.com/Python-Markdown/markdown Types: Product Added Reference Type MITRE: https://github.com/Python-Markdown/markdown/actions/runs/15736122892 Types: Product Added Reference Type MITRE: https://github.com/Python-Markdown/markdown/issues/1534 Types: Exploit, Issue Tracking -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Mar. 12, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-400 -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Mar. 06, 2026
Action Type Old Value New Value Added Reference http://www.openwall.com/lists/oss-security/2026/03/06/4 -
New CVE Received by [email protected]
Mar. 05, 2026
Action Type Old Value New Value Added 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. Added Reference https://github.com/Python-Markdown/markdown Added Reference https://github.com/Python-Markdown/markdown/actions/runs/15736122892 Added Reference https://github.com/Python-Markdown/markdown/issues/1534