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  4. CVE 2026 86433 commonmark 150 before 284 denial of service via
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Back to active CVEs
High · CVSS 8.7CVE-2026-86433

commonmark 1.5.0 before 2.8.4 Denial of Service via AttributesCVE-2026-86433

Answer in brief

CVE-2026-86433 records a High severity (CVSS 8.7) vulnerability in commonmark 1.5.0 before 2.8.4 Denial of Service via Attributes. The current sources do not mark it as known exploited. The current feed maps thephpleague/commonmark (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 7, 2026Updated Oct 8, 2026Source checked Oct 25, 2026First seen by HOL Sep 7, 2026Material review Oct 8, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 8.7
Exploitation
Not marked as known exploited
Affected software
1 mapped package or product
Fix availability
Available

Why this deserves its current priority

CVSS is 8.7. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps thephpleague/commonmark (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
thephpleague/commonmarkgeneric>=1.5.0 <2.8.42.8.4

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for thephpleague/commonmark.
  2. 2Review the reported fix. Update thephpleague/commonmark to 2.8.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Sep 7, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Oct 8, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Sep 7, 2026

Sources and claim methodology

  • GitHub security advisorygithub.com
  • Source referencevulncheck.com
Upstream source description

commonmark versions from 1.5.0 before 2.8.4 contain a denial of service vulnerability in the Attributes extension where AttributesListener::findTargetAndDirection() performs quadratic-time sibling list scanning. Unauthenticated attackers can submit approximately 32 KB of repeated attribute blocks to cause parsing to take over 5 seconds, exhausting server resources.

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Missing Auth
EPSS
Not reported
CWE IDs
CWE-407
Source
CVE List V5
Source checked
Oct 25, 2026
References
2 linked sources
Open source record