Flarum vulnerabilities

Flarum before 1.8.16 contains an improper session invalidation vulnerability that allows attackers who hold a valid session token to retain full account access after a victim changes their password, because the access_tokens table is never cleared on password change events. The TokensClearer::clearPasswordTokens() function only removes rows from the password_tokens table while leaving all active session cookies and API bearer tokens intact, including long-lived RememberAccessToken entries, and administrator-forced password resets via the user update endpoint are equally ineffective at revoking attacker-held sessions.

Flarum before 1.8.16 contains a password reset token expiry bypass vulnerability that allows unauthenticated attackers to reuse expired password reset tokens by submitting them directly to the reset processing endpoint. The SavePasswordController::handle() method calls PasswordToken::findOrFail() without performing any expiry validation, allowing attackers to bypass the 24-hour token lifetime enforced only during form rendering and change any account's password to gain an authenticated session.

In Flarum prior to versions 1.8.16 and 2.0.0-rc.1, the patch for CVE-2023-27577 restricted LESS @import and data-uri() features only in the custom_less setting, but not in other settings registered as LESS config variables (e.g., theme_primary_color, theme_secondary_color, and keys registered via Extend\Settings::registerLessConfigVar()). These values are interpolated verbatim into the LESS source at compile time, allowing an authenticated administrator to inject an arbitrary @import directive into the compiled forum.css. Since the LESS parser honors @import (inline) '<path>', an attacker can read arbitrary files reachable by the PHP process (LFI) or trigger outbound HTTP(S) requests (SSRF). The issue is patched in versions 1.8.16 and 2.0.0-rc.1.

Flarum, an open source forum software, is vulnerable to a Blind Server-Side Request Forgery (SSRF) attack and file disclosure on the server, even with a basic user account. By exploiting the vulnerability, an attacker can manipulate the application to execute unintended actions.