CVE-2026-41887

{
  "id": "CVE-2026-41887",
  "sourceIdentifier": "[email protected]",
  "published": "2026-05-08T17:16:30.890",
  "lastModified": "2026-10-26T18:10:00.173",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    },
    {
      "lang": "es",
      "value": "Flarum es un software de foro de código abierto. Antes de las versiones 1.8.16 y 2.0.0-rc.1, el parche de Flarum para CVE-2023-27577 restringía las características LESS @import y data-uri() en la configuración custom_less, pero la misma restricción nunca se aplicó a otras configuraciones registradas como variables de configuración LESS (por ejemplo, theme_primary_color y theme_secondary_color, así como cualquier clave registrada a través de Extend\\Settings::registerLessConfigVar()). Esos valores se interpolan literalmente en el código fuente LESS en tiempo de compilación, permitiendo a un administrador autenticado crear un valor de color de tema que inyecta una directiva @import arbitraria en el archivo forum.css compilado. Debido a que el analizador LESS subyacente respeta @import (inline) ’[path]’, un atacante puede leer ficheros arbitrarios accesibles por el proceso PHP (inclusión local de ficheros) o desencadenar peticiones HTTP(S) salientes (falsificación de petición del lado del servidor). Este problema ha sido parcheado en las versiones 1.8.16 y 2.0.0-rc.1."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "flarum",
          "product": "framework",
          "versions": [
            {
              "version": "< 1.8.16",
              "status": "affected"
            },
            {
              "version": ">= 2.0.0-beta.1, < 2.0.0-rc.1",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N",
          "baseScore": 4.9,
          "baseSeverity": "MEDIUM",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "HIGH",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "NONE",
          "availabilityImpact": "NONE"
        },
        "exploitabilityScore": 1.2,
        "impactScore": 3.6
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-05-08T19:26:06.629218Z",
          "id": "CVE-2026-41887",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-22"
        },
        {
          "lang": "en",
          "value": "CWE-918"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/flarum/framework/commit/2d90a1f19f0e46f8c7e1b07c48ba74b5e38f8410",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/flarum/framework/releases/tag/v1.8.16",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/flarum/framework/releases/tag/v2.0.0-rc.1",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/flarum/framework/security/advisories/GHSA-xjvc-pw2r-6878",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ]
}