Vulnerability-Lookup

ubuntu-cve-2026-86429

Vulnerability from osv_ubuntu

Published

2026-09-07 13:20

Modified

2026-09-16 11:43

Summary

Details

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.

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-2026-86429	REPORT
	https://www.cve.org/CVERecord?id=CVE-2026-86429	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": "The league/commonmark (thephpleague/commonmark) library in versions \u003e= 1.5.0 and \u003c 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 \u2014 such as text alternating with unpaired quotes, contiguous runs of block-level attribute blocks, or repeated class attributes \u2014 to trigger disproportionate CPU consumption and cause a denial of service. Fixed in 2.9.1.",
  "id": "UBUNTU-CVE-2026-86429",
  "modified": "2026-09-16T11:43:11Z",
  "published": "2026-09-07T13:20:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2026-86429"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-86429"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-jjv6-8j6v-6j52"
    }
  ],
  "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-2026-86429"
  ]
}

CVE-2026-86429 (GCVE-0-2026-86429)

Vulnerability from cvelistv5 – Published: 2026-09-07 12:53 – Updated: 2026-09-07 12:53

Title

commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes

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

CWE

CWE-407 - Inefficient Algorithmic Complexity

Assigner

VulnCheck mitre root

References

2 references

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

Impacted products

1 product

Vendor	Product	Version
thephpleague	commonmark	Affected: 1.5.0 , < 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

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "commonmark",
          "vendor": "thephpleague",
          "versions": [
            {
              "lessThan": "2.9.1",
              "status": "affected",
              "version": "1.5.0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "2.9.1",
              "versionType": "semver"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:thephpleague:commonmark:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "2.9.1",
                  "versionStartIncluding": "1.5.0",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "colinodell"
        }
      ],
      "datePublic": "2026-08-09T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "The league/commonmark (thephpleague/commonmark) library in versions \u003e= 1.5.0 and \u003c 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 \u2014 such as text alternating with unpaired quotes, contiguous runs of block-level attribute blocks, or repeated class attributes \u2014 to trigger disproportionate CPU consumption and cause a denial of service. Fixed in 2.9.1."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          },
          "format": "CVSS"
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-407",
              "description": "Inefficient Algorithmic Complexity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-07T12:53:49.905Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "name": "GitHub Security Advisory (GHSA-jjv6-8j6v-6j52)",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-jjv6-8j6v-6j52"
        },
        {
          "name": "VulnCheck Advisory: commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes",
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/commonmark-before-2.9.1-denial-of-service-via-smartpunct-and-attributes"
        }
      ],
      "title": "commonmark before 2.9.1 Denial of Service via SmartPunct and Attributes",
      "x_generator": {
        "engine": "vulncheck-endgame"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-86429",
    "datePublished": "2026-09-07T12:53:49.905Z",
    "dateReserved": "2026-09-07T12:33:13.368Z",
    "dateUpdated": "2026-09-07T12:53:49.905Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Detection rules are retrieved from Rulezet.

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

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.