{"id":"CVE-2026-41887","summary":"Flarum: Path traversal in LESS parser via theme color settings (incomplete fix for CVE-2023-27577)","details":"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) '\u003cpath\u003e', 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.","aliases":["GHSA-xjvc-pw2r-6878"],"modified":"2026-08-07T11:51:04.619998935Z","published":"2026-05-08T15:50:38.484Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-22","CWE-918"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41887.json"},"references":[{"type":"WEB","url":"https://github.com/flarum/framework/releases/tag/v1.8.16"},{"type":"WEB","url":"https://github.com/flarum/framework/releases/tag/v2.0.0-rc.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41887.json"},{"type":"ADVISORY","url":"https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41887"},{"type":"FIX","url":"https://github.com/flarum/framework/commit/2d90a1f19f0e46f8c7e1b07c48ba74b5e38f8410"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/flarum/framework","events":[{"introduced":"0"},{"introduced":"382991648c9db5d5e17476b55e4f9fe1cac1ea08"},{"fixed":"a2260e4a62f21591e1a9ae9b11c7db07c6507766"},{"fixed":"ebde06e404db0a5a52ff3507417037530c0371a8"},{"fixed":"2d90a1f19f0e46f8c7e1b07c48ba74b5e38f8410"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.8.16"},{"introduced":"2.0.0-beta.1"},{"fixed":"2.0.0-rc.1"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["v1.8.15","v2.0.0-beta.8","v1.8.14","v1.8.13","v2.0.0-beta.6","v1.8.12","v2.0.0-beta.5","v2.0.0-beta.4","v1.8.11","v2.0.0-beta.3","v1.8.10","v2.0.0-beta.2","v2.0.0-beta.1","v1.8.9","v1.8.8","v1.8.7","v1.8.6","v1.8.5","v1.8.3","v1.8.2","v1.8.1","v1.8.0","v1.7.1","v1.7.0","v1.6.1","v1.6.0","v1.5.0","v1.4.0","v1.3.1","v1.3.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-41887.json"}}],"schema_version":"1.8.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N"}]}