league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes

{
  "id": "b826568df748028b84e1f5fa77919436e98fd37c7adb466b4f05ee5761041969",
  "url": "https://osv.dev/vulnerability/CVE-2026-71478",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes",
    "summary": "league/commonmark is a PHP library for parsing and rendering CommonMark Markdown. From 1.5.0 until 2.9.0, the AttributesExtension's href and src unsafe-link filter can be bypassed by embedding control bytes, such as a tab, carriage return, line feed, or leading C0 control character, in a javascript: URL that browsers discard before parsing the scheme, causing the browser to still execute the script even when the unsafe-link filter is enabled. This issue is fixed in 2.9.0.",
    "evidence": "osv:CVE-2026-71478",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-71478",
      "aliases": [
        "CVE-2026-71478",
        "GHSA-29pj-957v-52mc"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/thephpleague/commonmark",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fc33ca12575e98e57cdce7d5f38b2ca5335714b3"
                },
                {
                  "fixed": "493a5aa7d65754b73846006eaff9c2c4431a8e2c"
                },
                {
                  "fixed": "5703d83ba3da3b2e356a5fedc848ed6d8ffb6529"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "1.5.0"
                      },
                      {
                        "last_affected": "2.8.3"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "493a5aa7d65754b73846006eaff9c2c4431a8e2c"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "5703d83ba3da3b2e356a5fedc848ed6d8ffb6529"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "2.9.0"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-71478.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:21.813656968Z",
      "provider": "osv",
      "references": [
        "https://github.com/thephpleague/commonmark/releases/tag/2.9.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71478.json",
        "https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-71478",
        "https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-692",
          "CWE-79",
          "CWE-86"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/71xxx/CVE-2026-71478.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-71478",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 488264,
  "published_at": "2026-08-06T20:30:32.045+00:00"
}