{"id":"CVE-2026-41887","state":"PUBLISHED","title":"Flarum: Path traversal in LESS parser via theme color settings (incomplete fix for CVE-2023-27577)","description":"Flarum is open-source forum software. Prior to versions 1.8.16 and 2.0.0-rc.1, Flarum's patch for CVE-2023-27577 restricted the @import and data-uri() LESS features in the custom_less setting, but the same restriction was never applied to other settings registered as LESS config variables (for example theme_primary_color and theme_secondary_color, as well as any key registered via Extend\\Settings::registerLessConfigVar()). Those values are interpolated verbatim into the LESS source at compile time, allowing an authenticated administrator to craft a theme-color value that injects an arbitrary @import directive into the compiled forum.css. Because the underlying LESS parser honours @import (inline) '<path>', an attacker can read arbitrary files reachable by the PHP process (local file inclusion) or trigger outbound HTTP(S) requests (server-side request forgery). This issue has been patched in versions 1.8.16 and 2.0.0-rc.1.","publishedAt":"2026-05-08T15:50:38.484Z","updatedAt":"2026-05-08T19:26:53.642Z","severity":{"score":4.9,"label":"Medium","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["flarum framework"],"affected":[{"vendor":"flarum","product":"framework","versions":[{"version":"< 1.8.16","status":"affected"},{"version":">= 2.0.0-beta.1, < 2.0.0-rc.1","status":"affected"}]}],"references":["https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878","https://github.com/flarum/framework/commit/2d90a1f19f0e46f8c7e1b07c48ba74b5e38f8410","https://github.com/flarum/framework/releases/tag/v1.8.16","https://github.com/flarum/framework/releases/tag/v2.0.0-rc.1"],"weaknesses":["CWE-22","CWE-918"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/41xxx/CVE-2026-41887.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-41887","state":"PUBLISHED","datePublished":"2026-05-08T15:50:38.484Z","dateUpdated":"2026-05-08T19:26:53.642Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-04-22T15:11:54.671Z"},"containers":{"cna":{"title":"Flarum: Path traversal in LESS parser via theme color settings (incomplete fix for CVE-2023-27577)","descriptions":[{"lang":"en","value":"Flarum is open-source forum software. Prior to versions 1.8.16 and 2.0.0-rc.1, Flarum's patch for CVE-2023-27577 restricted the @import and data-uri() LESS features in the custom_less setting, but the same restriction was never applied to other settings registered as LESS config variables (for example theme_primary_color and theme_secondary_color, as well as any key registered via Extend\\Settings::registerLessConfigVar()). Those values are interpolated verbatim into the LESS source at compile time, allowing an authenticated administrator to craft a theme-color value that injects an arbitrary @import directive into the compiled forum.css. Because the underlying LESS parser honours @import (inline) '<path>', an attacker can read arbitrary files reachable by the PHP process (local file inclusion) or trigger outbound HTTP(S) requests (server-side request forgery). This issue has been patched in versions 1.8.16 and 2.0.0-rc.1."}],"affected":[{"vendor":"flarum","product":"framework","versions":[{"version":"< 1.8.16","status":"affected"},{"version":">= 2.0.0-beta.1, < 2.0.0-rc.1","status":"affected"}]}],"references":[{"url":"https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878","name":"https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/flarum/framework/commit/2d90a1f19f0e46f8c7e1b07c48ba74b5e38f8410","name":"https://github.com/flarum/framework/commit/2d90a1f19f0e46f8c7e1b07c48ba74b5e38f8410","tags":["x_refsource_MISC"]},{"url":"https://github.com/flarum/framework/releases/tag/v1.8.16","name":"https://github.com/flarum/framework/releases/tag/v1.8.16","tags":["x_refsource_MISC"]},{"url":"https://github.com/flarum/framework/releases/tag/v2.0.0-rc.1","name":"https://github.com/flarum/framework/releases/tag/v2.0.0-rc.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":4.9,"baseSeverity":"MEDIUM","confidentialityImpact":"HIGH","integrityImpact":"NONE","privilegesRequired":"HIGH","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-22","lang":"en","description":"CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-918","lang":"en","description":"CWE-918: Server-Side Request Forgery (SSRF)","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-05-08T15:50:38.484Z"},"source":{"advisory":"GHSA-xjvc-pw2r-6878","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-08T19:26:06.629218Z","id":"CVE-2026-41887","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":"2026-05-08T19:26:53.642Z"}}]}}}