CVE-2026-41887: medium-severity vulnerability in flarum framework
Flarum: Path traversal in LESS parser via theme color settings (incomplete fix for CVE-2023-27577)
Published
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 4.9epss 0.5%
exploitation probability
0.5%top 59% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Affected products
flarum · frameworkRelated CVEs — flarum framework
In the same product, most dangerous first.
CVE-2024-21641MEDIUMFlarum's Logout Route allows open redirectsEPSS 1.1%CVE-2023-27577MEDIUMPath Traversal Vulnerability in `LESS` Parser allows reading of sensitive server files in flarumEPSS 0.9%CVE-2022-41938CRITICALCross site scripting vulnerability with discussion titles in flarumEPSS 0.8%CVE-2023-22487HIGHPost mentions can be used to read any post on the forum without access controlEPSS 0.7%CVE-2023-22489LOWFlarum is missing authorization in discussion repliesEPSS 0.6%CVE-2025-27794MEDIUMFlarum Vulnerable to Session Hijacking via Authoritative Subdomain Cookie OverwriteEPSS 0.5%