{"id":"CVE-2026-71478","state":"PUBLISHED","title":"league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes","description":"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.","publishedAt":"2026-08-06T20:30:32.045Z","updatedAt":"2026-08-07T17:05:57.244Z","severity":{"score":6.1,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["thephpleague commonmark"],"affected":[{"vendor":"thephpleague","product":"commonmark","versions":[{"version":">= 1.5.0, <= 2.8.3","status":"affected"}]}],"references":["https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c","https://github.com/thephpleague/commonmark/releases/tag/2.9.0"],"weaknesses":["CWE-79","CWE-86","CWE-692"],"ingestedAt":"2026-10-29T20:12:49.727Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/71xxx/CVE-2026-71478.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-71478","state":"PUBLISHED","datePublished":"2026-08-06T20:30:32.045Z","dateUpdated":"2026-08-07T17:05:57.244Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-08-06T19:56:23.724Z"},"containers":{"cna":{"title":"league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"thephpleague","product":"commonmark","versions":[{"version":">= 1.5.0, <= 2.8.3","status":"affected"}]}],"references":[{"url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","name":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c","name":"https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c","tags":["x_refsource_MISC"]},{"url":"https://github.com/thephpleague/commonmark/releases/tag/2.9.0","name":"https://github.com/thephpleague/commonmark/releases/tag/2.9.0","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":6.1,"baseSeverity":"MEDIUM","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"CHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-79","lang":"en","description":"CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-86","lang":"en","description":"CWE-86: Improper Neutralization of Invalid Characters in Identifiers in Web Pages","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-692","lang":"en","description":"CWE-692: Incomplete Denylist to Cross-Site Scripting","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-08-06T20:30:32.045Z"},"source":{"advisory":"GHSA-29pj-957v-52mc","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-07T17:04:55.894840Z","id":"CVE-2026-71478","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-07T17:05:57.244Z"}}]}}}