Server-side Request Forgery (SSRF) Affecting flarum/core package, versions <1.8.16>=2.0.0-beta.1, <2.0.0-rc.1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published27 Apr 2026
- disclosed22 Apr 2026
- creditUnknown
Introduced: 22 Apr 2026
CVE-2026-41887 (opens in a new tab)How to fix?
Upgrade flarum/core to version 1.8.16, 2.0.0-rc.1 or higher.
Overview
flarum/core is a simple discussion platform for your website.
Affected versions of this package are vulnerable to Server-side Request Forgery (SSRF) via the interpolation of unvalidated LESS config variables during CSS compilation. An attacker can access arbitrary files on the server or initiate outbound HTTP(S) requests by injecting malicious @import directives into theme color settings. This is only exploitable if the attacker has administrator privileges.
Workaround
This vulnerability can be mitigated by protecting administrator accounts with strong, unique passwords, enabling two-factor authentication where supported, restricting administrator access to trusted users, and reviewing the public CSS output for unexpected content.