CVE-2025-69534Public exploitNetwork attack vector

Service interrupt via incomplete HTML declaration

Published Mar 5, 2026 · Updated Mar 5, 2026

Reachable assertion in Python-Markdown before 3.8.1 allows remote attackers to crash Markdown-processing applications with malformed raw HTML. The parse_html_declaration handlers pass non-CDATA <![ sequences to HTMLParser, whose assertion escapes uncaught instead of treating them as bogus comments. Exploitation requires an application to render attacker-controlled Markdown; applications that expose uncaught exception traces also disclose stack details.

CVSS severity7.5
High
EPSS probability0.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in Python-Markdown before 3.8.1 allows remote attackers to crash Markdown-processing applications with malformed raw HTML. The parse_html_declaration handlers pass non-CDATA <![ sequences to HTMLParser, whose assertion escapes uncaught instead of treating them as bogus comments. Exploitation requires an application to render attacker-controlled Markdown; applications that expose uncaught exception traces also disclose stack details.

The record

CVE
CVE-2025-69534
Published
Mar 5, 2026
Updated
Mar 5, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-248, CWE-400, CWE-617, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.2redhat-SADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
8.7SUSECVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5SUSECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-248Uncaught Exception
CWE-400Uncontrolled Resource Consumption
CWE-617Reachable Assertion
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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