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🛡️ CVE-2025-69534 — markdown

🟠 CVSS 7.5 — High ⚠️ Exploit Public CWE-248 OSV
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Python-Markdown has an Uncaught Exception

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: None — an unauthenticated stranger can try it.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: None.
  • Integrity impact: None.
  • Availability impact: High — total loss, or loss the attacker controls.

Weakness class

CVE-2025-69534 is classified as CWE-248: Uncaught Exception. An exception is thrown from a function, but it is not caught.

Affected software

CVE-2025-69534 is recorded against 1 package.

  • markdown

Timeline and source

Published on 5 March 2026 and last revised on 15 July 2026. A public exploit is known to exist, which raises the urgency of patching considerably. Record sourced from OSV.

References

github.com (Web)
www.openwall.com (Advisory)
github.com (Report)
github.com (Package)
github.com (Advisory)

Other advisories for this package

markdown has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-248: Uncaught Exception) in other software:

Details

Severity HIGH
CVSS Score 7.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-248
Public Exploit ⚠️ Yes
Source OSV
Published 2026-03-05
Updated 2026-08-20
Modified 2026-07-15
Fix URL N/A

Affected Packages

Software From version Fixed in
markdown — —

Exploit Protection

Are you running markdown?

CVE-2025-69534 carries CVSS 7.5 High rating and a public exploit already exists. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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