CVE-2023-40033
HighCVSS 7.1Exploitation Probability (EPSS)
Low risk34th percentile - higher than 34% of all known CVEs
Summary
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.
Risk Assessment
Organizations may be exposed to the disclosure of sensitive data and the potential for SSRF attacks, which could lead to further system compromises.
Recommendation
It is recommended to upgrade Flarum to version 1.8.0, which includes security patches. Users unable to upgrade should temporarily disable `allow_url_fopen` in PHP to mitigate the SSRF risk.
Other vulnerabilities in Flarum
See all- CVE-2026-39924Medium
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.
- CVE-2026-39923High
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.
Original NVD description (English source)
Flarum is an open source forum software. Flarum is affected by a vulnerability that allows an attacker to conduct a Blind Server-Side Request Forgery (SSRF) attack or disclose any file on the server, even with a basic user account on any Flarum forum. By uploading a file containing a URL and spoofing the MIME type, an attacker can manipulate the application to execute unintended actions. The vulnerability is due to the behavior of the `intervention/image` package, which attempts to interpret the supplied file contents as a URL, which then fetches its contents. This allows an attacker to exploit the vulnerability to perform SSRF attacks, disclose local file contents, or conduct a blind oracle attack. This has been patched in Flarum version 1.8.0. Users are advised to upgrade. Users unable to upgrade may disable PHP's `allow_url_fopen` which will prevent the fetching of external files via URLs as a temporary workaround for the SSRF aspect of the vulnerability.