CVE-2026-86429 Vulnerability Analysis & Exploit Details

CVE-2026-86429
Vulnerability Scoring

7.5
/10
Very High Risk

Highly exploitable, CVE-2026-86429 poses a critical security risk that could lead to severe breaches.

Attack Complexity Details

  • Attack Complexity: Low
    Exploits can be performed without significant complexity or special conditions.
  • Attack Vector: Network
    Vulnerability is exploitable over a network without physical access.
  • Privileges Required: None
    No privileges are required for exploitation.
  • Scope: Unchanged
    Exploit remains within the originally vulnerable component.
  • User Interaction: None
    No user interaction is necessary for exploitation.

CVE-2026-86429 Details

Status: Analyzed

Last updated: 🕓 09 Sep 2026, 16:29 UTC
Originally published on: 🕐 07 Sep 2026, 13:20 UTC

Time between publication and last update: 2 days

CVSS Release: version 3

CVSS3 Source

disclosure@vulncheck.com

CVSS3 Type

Primary

CVSS3 Vector

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

CVE-2026-86429 Vulnerability Summary

CVE-2026-86429: The league/commonmark (thephpleague/commonmark) library in versions >= 1.5.0 and < 2.9.1 contains quadratic parsing complexity in its SmartPunctExtension and AttributesExtension. When either extension is explicitly registered on the Environment (they are not enabled by default and are excluded from the standard CommonMark and GitHub-Flavored Markdown converters), an unauthenticated attacker can submit small, specially crafted Markdown documents — such as text alternating with unpaired quotes, contiguous runs of block-level attribute blocks, or repeated class attributes — to trigger disproportionate CPU consumption and cause a denial of service. Fixed in 2.9.1.

Assessing the Risk of CVE-2026-86429

Access Complexity Graph

The exploitability of CVE-2026-86429 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2026-86429

With low attack complexity and no required privileges, CVE-2026-86429 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2026-86429, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2026-86429, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: None
    CVE-2026-86429 has no significant impact on data confidentiality.
  • Integrity: None
    CVE-2026-86429 poses no threat to data integrity.
  • Availability: High
    CVE-2026-86429 can disrupt system operations, potentially causing complete denial of service (DoS).

CVE-2026-86429 References

External References

CWE Common Weakness Enumeration

CWE-407

Vulnerable Configurations

  • cpe:2.3:a:thephpleague:commonmark:1.5.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.4:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.4:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.5:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.5:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.6:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.6:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.7:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.7:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.5.8:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.5.8:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.4:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.4:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.5:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.5:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.6:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.6:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:1.6.7:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:1.6.7:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.0:-:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.0:-:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.0:rc1:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.0:rc1:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.0:rc2:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.0:rc2:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.0:beta1:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.0:beta1:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.0:beta2:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.0:beta2:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.0:beta3:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.0:beta3:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.0.4:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.0.4:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.1.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.1.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.1.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.1.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.1.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.1.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.1.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.1.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.2.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.2.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.2.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.2.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.2.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.2.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.2.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.2.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.2.4:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.2.4:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.2.5:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.2.5:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.4:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.4:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.5:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.5:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.6:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.6:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.7:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.7:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.8:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.8:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.3.9:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.3.9:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.4.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.4.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.4.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.4.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.4.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.4.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.4.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.4.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.4.4:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.4.4:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.5.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.5.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.5.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.5.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.5.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.5.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.5.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.5.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.6.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.6.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.6.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.6.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.6.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.6.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.7.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.7.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.7.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.7.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.8.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.8.0:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.8.1:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.8.1:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.8.2:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.8.2:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.8.3:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.8.3:*:*:*:*:*:*:*
  • cpe:2.3:a:thephpleague:commonmark:2.9.0:*:*:*:*:*:*:*
    cpe:2.3:a:thephpleague:commonmark:2.9.0:*:*:*:*:*:*:*

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