{"api_version":"1","generated_at":"2026-08-07T04:18:42+00:00","cve":"CVE-2026-71478","urls":{"html":"https://cve.report/CVE-2026-71478","api":"https://cve.report/api/cve/CVE-2026-71478.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-71478","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-71478"},"summary":{"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.","state":"PUBLISHED","assigner":"GitHub_M","published_at":"2026-08-06 22:18:31","updated_at":"2026-08-06 22:18:31"},"problem_types":["CWE-79","CWE-86","CWE-692","CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","CWE-86 CWE-86: Improper Neutralization of Invalid Characters in Identifiers in Web Pages","CWE-692 CWE-692: Incomplete Denylist to Cross-Site Scripting"],"metrics":[{"version":"3.1","source":"security-advisories@github.com","type":"Secondary","score":"6.1","severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","baseScore":6.1,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"CHANGED","confidentialityImpact":"LOW","integrityImpact":"LOW","availabilityImpact":"NONE"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"6.1","severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","data":{"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"}}],"references":[{"url":"https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c","name":"https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","name":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/thephpleague/commonmark/releases/tag/2.9.0","name":"https://github.com/thephpleague/commonmark/releases/tag/2.9.0","refsource":"security-advisories@github.com","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-71478","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-71478","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"thephpleague","product":"commonmark","version":"affected >= 1.5.0, <= 2.8.3","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"product":"commonmark","vendor":"thephpleague","versions":[{"status":"affected","version":">= 1.5.0, <= 2.8.3"}]}],"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."}],"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","description":"CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-86","description":"CWE-86: Improper Neutralization of Invalid Characters in Identifiers in Web Pages","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-692","description":"CWE-692: Incomplete Denylist to Cross-Site Scripting","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-08-06T20:30:32.045Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M"},"references":[{"name":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc","tags":["x_refsource_CONFIRM"],"url":"https://github.com/thephpleague/commonmark/security/advisories/GHSA-29pj-957v-52mc"},{"name":"https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c","tags":["x_refsource_MISC"],"url":"https://github.com/thephpleague/commonmark/commit/493a5aa7d65754b73846006eaff9c2c4431a8e2c"},{"name":"https://github.com/thephpleague/commonmark/releases/tag/2.9.0","tags":["x_refsource_MISC"],"url":"https://github.com/thephpleague/commonmark/releases/tag/2.9.0"}],"source":{"advisory":"GHSA-29pj-957v-52mc","discovery":"UNKNOWN"},"title":"league/commonmark: AttributesExtension href/src unsafe-link filter bypass via embedded control bytes"}},"cveMetadata":{"assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","assignerShortName":"GitHub_M","cveId":"CVE-2026-71478","datePublished":"2026-08-06T20:30:32.045Z","dateReserved":"2026-08-06T19:56:23.724Z","dateUpdated":"2026-08-06T20:30:32.045Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-08-06 22:18:31","lastModifiedDate":"2026-08-06 22:18:31","problem_types":["CWE-79","CWE-86","CWE-692","CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","CWE-86 CWE-86: Improper Neutralization of Invalid Characters in Identifiers in Web Pages","CWE-692 CWE-692: Incomplete Denylist to Cross-Site Scripting"],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","baseScore":6.1,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"CHANGED","confidentialityImpact":"LOW","integrityImpact":"LOW","availabilityImpact":"NONE"},"exploitabilityScore":2.8,"impactScore":2.7}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"71478","Ordinal":"1","Title":"league/commonmark: AttributesExtension href/src unsafe-link filt","CVE":"CVE-2026-71478","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"71478","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"league/commonmark: AttributesExtension href/src unsafe-link filt"}]}}}