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CVE Record

CVE-2025-69534: Python-Markdown version 3.8 contain a vulnerability where malformed HTML-like sequences can cause html.pars...

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.

HighCVSS 8.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Python-Markdown 3.8 can crash when parsing certain malformed HTML-like Markdown. Any public-facing service that accepts and renders untrusted Markdown could be knocked offline. The sources say this is fixed in 3.8.1. No cited source indicates active exploitation or CISA KEV listing.

Executive priority

Prioritize patching internet-facing or business-critical Markdown rendering services. This is a high-availability risk, not a confirmed data-compromise event. The fix is identified, and remediation should be straightforward once affected Python-Markdown usage is found.

Technical view

The flaw is an unhandled AssertionError raised by html.parser.HTMLParser during Python-Markdown parsing. Python-Markdown 3.8 does not catch it, causing denial of service and possible information disclosure through uncaught exceptions. CVSS is 8.2, network exploitable, unauthenticated, low complexity, with high availability impact.

Likely exposure

Exposure is most likely in web apps, documentation platforms, CI/CD jobs, or internal services that parse attacker-controlled Markdown using Python-Markdown 3.8. The source bundle’s affected CPE metadata is incomplete, so confirm exact package names and downstream vendor status in your environment.

Exploitation context

The sources describe remote unauthenticated denial of service from attacker-controlled Markdown input. They do not provide evidence of public exploitation, active exploitation, or KEV inclusion. Treat internet-facing Markdown renderers as higher priority because a crash can affect availability without authentication.

Researcher notes

Key gaps are affected CPE/product mapping and real-world exploit telemetry. Validate exposure by dependency inventory and data-flow review rather than assuming every Python application is affected. Focus on untrusted Markdown parsing paths and downstream vendor package status.

Mitigation direction

  • Upgrade Python-Markdown to version 3.8.1 or later where applicable.
  • Apply relevant Red Hat advisories for managed downstream packages.
  • Avoid rendering untrusted Markdown until patched, where business impact allows.
  • Ensure parser exceptions are handled without exposing stack traces.
  • Check vendor guidance for product-specific backports or mitigations.

Validation and detection

  • Inventory applications and pipelines using Python-Markdown.
  • Confirm whether version 3.8 is present in runtime and build environments.
  • Identify routes, APIs, or jobs that parse user-controlled Markdown.
  • Review logs for uncaught AssertionError during Markdown parsing.
  • Verify patched deployments use 3.8.1 or vendor-fixed builds.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-400: Exact CWE lookup

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cwe · low confidence lookup

CWE-617: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cve · low confidence lookup

CVE-2025-69534 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.2 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
3ADP providers
20Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.2CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H3.94.2redhat-SADP
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

8.2High
CVSS 3.1 vector shape for CVE-2025-69534Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
redhat-SADPpython-markdown: denial of service via malformed HTML-like sequences
other:Red Hat severity ratingcvssV3_1
  • 2026-03-05T16:01:10.432Z: Reported to Red Hat.
  • 2026-03-05T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

CWE-400CWE-617

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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CWE-617 · source CWE mapping

Reachable Assertion

Reachable Assertion represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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