Local File Inclusion in Flarum Forum Software due to Insecure LESS Configuration
CVE-2026-41887

4.9MEDIUM

Key Information:

Vendor

Flarum

Status
Framework
Vendor
CVE Published:
8 May 2026

What is CVE-2026-41887?

Flarum, an open-source forum software, has a vulnerability that arises from insufficient restrictions on LESS configuration settings. Specifically, the limitations intended for the custom_less setting were not universally applied, allowing authenticated administrators to exploit theme color values. By injecting an arbitrary @import directive into compiled CSS, an attacker could leverage this to execute local file inclusions or trigger unauthorized outbound HTTP requests. This vulnerability has been addressed in Flarum versions 1.8.16 and 2.0.0-rc.1, underscoring the importance of keeping software updated to mitigate exploitation risks.

Affected Version(s)

framework < 1.8.16 < 1.8.16

framework >= 2.0.0-beta.1, < 2.0.0-rc.1 < 2.0.0-beta.1, 2.0.0-rc.1

References

https://github.com/flarum/framework/security/advisories/G...
x_refsource_CONFIRM
https://github.com/flarum/framework/commit/2d90a1f19f0e46...
x_refsource_MISC
https://github.com/flarum/framework/releases/tag/v1.8.16
x_refsource_MISC

CVSS V3.1

Score:
4.9
Severity:
MEDIUM
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
High
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.