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CVE-2025-69534

Python-markdown Markdown denial of service

7.5 HIGHPublic exploitEPSS 0.59%
  1. Published5 Mar 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Python-markdown Markdown3.8

Remediation

No fixed version is recorded in the NVD data. Check the vendor advisory for the latest guidance.

References

and 10 more references

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Frequently asked

Is CVE-2025-69534 being actively exploited?

CVE-2025-69534 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.59%.

How severe is CVE-2025-69534?

CVE-2025-69534 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.59% probability of exploitation.

Which products are affected by CVE-2025-69534?

Affected products include Python-markdown Markdown.

How do I fix CVE-2025-69534?

Apply the vendor's patch or advisory guidance, then verify no affected versions remain across your devices.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2025-69534 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.