Vulnerability-Lookup

UBUNTU-CVE-2026-86430 (CVE-2026-86430)

Vulnerability from osv_ubuntu – Published: 2026-09-07 13:20 – Updated: 2026-09-16 11:43 – Source website

Details

league/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code block detection, reference link label lookup, and emphasis delimiter processing that perform super-linear work on crafted input. Attackers can submit specially crafted Markdown with long backtick runs, nested brackets, or delimiter sequences to consume disproportionate CPU time and prevent legitimate requests from completing.

Severity

7.5 (High)


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

8.7 (High)


                    
                      CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2026-86430	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-86430	REPORT
	https://github.com/thephpleague/commonmark/securi…	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "php-league-commonmark",
            "binary_version": "1.3.1-1ubuntu2+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "php-league-commonmark",
        "purl": "pkg:deb/ubuntu/php-league-commonmark@1.3.1-1ubuntu2+esm1?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.1.2-1",
        "1.2.0-1",
        "1.3.0-1",
        "1.3.1-1",
        "1.3.1-1ubuntu2",
        "1.3.1-1ubuntu2+esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "php-league-commonmark",
            "binary_version": "1.6.7-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:22.04:LTS",
        "name": "php-league-commonmark",
        "purl": "pkg:deb/ubuntu/php-league-commonmark@1.6.7-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "1.5.7-2build1",
        "1.6.6-1build1",
        "1.6.7-1",
        "1.6.7-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "php-league-commonmark",
            "binary_version": "2.4.2-2ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:24.04:LTS",
        "name": "php-league-commonmark",
        "purl": "pkg:deb/ubuntu/php-league-commonmark@2.4.2-2ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/noble"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.3.9-1",
        "2.4.1-1",
        "2.4.2-1",
        "2.4.2-2",
        "2.4.2-2ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "php-league-commonmark",
            "binary_version": "2.8.0-1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:26.04:LTS",
        "name": "php-league-commonmark",
        "purl": "pkg:deb/ubuntu/php-league-commonmark@2.8.0-1?arch=source\u0026distro=resolute"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.7.0-1",
        "2.7.1-2",
        "2.8.0-1"
      ]
    }
  ],
  "aliases": [],
  "details": "league/commonmark versions before 2.9.1 contain multiple denial of service vulnerabilities in fenced code block detection, reference link label lookup, and emphasis delimiter processing that perform super-linear work on crafted input. Attackers can submit specially crafted Markdown with long backtick runs, nested brackets, or delimiter sequences to consume disproportionate CPU time and prevent legitimate requests from completing.",
  "id": "UBUNTU-CVE-2026-86430",
  "modified": "2026-09-16T11:43:11Z",
  "published": "2026-09-07T13:20:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-86430"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-86430"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-j8pm-gj4c-rq4x"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2026-86430"
  ]
}

CVE-2026-86430 (GCVE-0-2026-86430)

Vulnerability from cvelistv5 – Published: 2026-09-07 12:53 – Updated: 2026-10-08 15:25

Title

league/commonmark before 2.9.1 Denial of Service via parsing

Summary

Severity

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-09 14:31 UTC

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

VulnCheck CNA under the mitre root

CNA scorecard B 84/100 over 7416 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/thephpleague/commonmark/securi…	vendor-advisory
https://www.vulncheck.com/advisories/league-commo…	third-party-advisory

Impacted products

1 product

Vendor	Product	Version
thephpleague	commonmark	Affected: 0.6.0 , < 2.9.1 (semver) Unaffected: 2.9.1 (semver) cpe:2.3:a:thephpleague:commonmark::::::::

Date Public

2026-08-09 00:00

Credits

colinodell

Show details on NVD website

JSON

To clipboard

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                "id": "CVE-2026-86430",
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                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-09T14:31:04.144121Z",
                "version": "2.0.3"
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      "metrics": [
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            "privilegesRequired": "NONE",
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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