HighCVE-2025-69534

    Python-markdown Markdown: Information Disclosure (CVE-2025-69534)

    Published Last modified Sources: Red Hat, Ubuntu, Debian LTS, BSI, CVE.org, OSV

    What is affected, what to do

    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.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Affected
    • Python-markdown Markdown eq 3.8..3.8

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    7.5

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    7.5

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: Red Hat, Ubuntu, Debian LTS, BSI, CVE.org, OSV

    0.6 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 48.6

    Show all metrics
    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    71.29 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    7.5 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.5
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.6 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    48.6
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    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.

    Source: redhat_csaf, Ubuntu Security Notices, Debian LTS Advisories, BSI WID Portal, BSI CSAF, NVD (NIST), OSV (Open Source Vulnerabilities), CVE.org (MITRE), cvelistv5

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    python-markdownmarkdown
    • 3.8
    • —
    Red HatEnterprise Linux
    • 9.6
    • 10
    • 9
    • 9.4
    • —
    • —
    • —
    • —
    pypimarkdown
    • 2.6.1
    • 2.6.7
    • 2.6.3
    • 2.1.1
    • 1.7
    • 3.4.3
    • 3.3.5
    • 2.6.10
    • 3.3.7
    • 2.0
    • 3.2.1
    • 2.6.11
    • 2.5.1
    • 3.3.4
    • 2.6.8
    • 3.1.1
    • 2.4
    • 3.0.1
    • 3.2
    • 2.6.6
    • 3.8
    • 2.6
    • 2.0.2
    • 3.3.6
    • 3.0
    • 2.5
    • 3.1
    • 3.2.2
    • 2.3.1
    • 3.5.2
    • 3.5.1
    • 3.3
    • 2.0.3
    • 2.2.0
    • 3.4.1
    • 2.6.9
    • 2.3
    • 2.2.1
    • 3.4
    • 3.3.2
    • 3.7
    • 2.5.2
    • 3.4.4
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    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianpython3.11bookworm

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedMITRE

      Show 9 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/Python-Markdown/markdown
      Referenceadded
      —
      https://github.com/Python-Markdown/markdown/actions/runs/15736122892
      Referenceadded
      —
      https://github.com/Python-Markdown/markdown/issues/1534
      Referenceremoved
      https://github.com/Python-Markdown/markdown
      —
      Referenceremoved
      https://github.com/Python-Markdown/markdown/actions/runs/15736122892
      —
      Referenceremoved
      https://github.com/Python-Markdown/markdown/issues/1534
      —
      Reference typeremoved
      https://github.com/Python-Markdown/markdown Types: Product
      —
      Reference typeremoved
      https://github.com/Python-Markdown/markdown/actions/runs/15736122892 Types: Product
      —
      Reference typeremoved
      https://github.com/Python-Markdown/markdown/issues/1534 Types: Exploit, Issue Tracking
      —

      Source identifier: cve@mitre.org

    2. Record modifiedCVE Program

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      http://www.openwall.com/lists/oss-security/2026/03/06/4
      Referenceremoved
      http://www.openwall.com/lists/oss-security/2026/03/06/4
      —
      Reference typeremoved
      http://www.openwall.com/lists/oss-security/2026/03/06/4 Types: Mailing List, Third Party Advisory
      —

      Source identifier: af854a3a-2127-422b-91ae-364da2661108

    3. Record modifiedRed Hat ADP

      Show 33 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2025/69xxx/CVE-2025-69534.json">CVE-2025-69534</a>
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:10184
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:13508
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:13512
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:13826
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:14835
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:14873
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:14874
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:19155
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:19366
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:20674
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:20676
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:20677
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:9742
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2025-69534
      Referenceadded
      —
      https://bugzilla.redhat.com/show_bug.cgi?id=2444839
      Referenceadded
      —
      https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-69534.json
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:10184
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:13508
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:13512
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:13826
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:14835
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:14873
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:14874
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:19155
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:19366
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:20674
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:20676
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:20677
      —
      Referenceremoved
      https://access.redhat.com/errata/RHSA-2026:9742
      —
      Referenceremoved
      https://access.redhat.com/security/cve/CVE-2025-69534
      —
      Referenceremoved
      https://bugzilla.redhat.com/show_bug.cgi?id=2444839
      —
      Referenceremoved
      https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-69534.json
      —

      Source identifier: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

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