Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Scope (S:U) | Scope unchanged |
| Confidentiality (C:N) | No confidentiality impact |
| Integrity (I:N) | No integrity impact |
| Availability (A:H) | High availability impact |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
About Python-Markdown Markdown
CVE-2025-69534 affects Python-Markdown Markdown, a product from Python-Markdown. Before acting, confirm where Python-Markdown Markdown runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: 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.
The weakness class is Uncontrolled Resource Consumption. An attacker can exhaust CPU, memory or connections.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Python-Markdown Markdown |
| Affected versions | Markdown 3.8 |
| Published | Mar 5, 2026 |
| Last modified | Sep 7, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | cve@mitre.org |
How to detect it
- Inventory every instance of Python-Markdown Markdown and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Python-Markdown Markdown named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Python-Markdown Markdown to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-400: Uncontrolled Resource Consumption More CVEs with this weakness
- CWE-617 More CVEs with this weakness
Technical References
- ▸NVD entry
- ▸CVE.org record
- ▸GitHub repository reference
- ▸GitHub repository reference
- ▸GitHub issue or pull request
- ▸Openwall oss security mailing list
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
- ▸Red Hat security advisory
Frequently asked questions
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