CVE-2026-41887 — Server-Side Request Forgery

title: CVE-2026-41887 - Flarum LESS Config Var SSRF/LFI via @import
id: scw-2026-05-08-ai-1
status: experimental
level: critical
description: |
  Detects an authenticated administrator attempting to exploit CVE-2026-41887 in Flarum by injecting an @import directive into the theme_primary_color setting. This can lead to Local File Inclusion (LFI) or Server-Side Request Forgery (SSRF) by causing the server to compile LESS code that includes arbitrary files or makes outbound requests.
author: SCW Feed Engine (AI-generated)
date: 2026-05-08
references:
  - https://shimiscyberworld.com/posts/nvd-CVE-2026-41887/
tags:
  - attack.lateral_movement
  - attack.t1071.001
logsource:
    category: webserver
detection:
  selection:
      cs-uri|contains:
          - '/admin/settings/theme'
      cs-method:
          - 'POST'
      cs-uri-query|contains:
          - 'theme_primary_color'
      cs-uri-query|contains:
          - '@import'
  selection_base:
      cs-uri|contains:
          - '/admin/settings/theme'
      cs-method:
          - 'POST'
  selection_indicators:
      cs-uri-query|contains:
          - 'theme_primary_color'
      cs-uri-query|contains:
          - '@import'
  condition: selection_base AND selection_indicators
falsepositives:
  - Legitimate administrative activity

Source: Shimi's Cyber World · License & reuse