Source: cve@mitre.org
Backdoor in auth.php3 in Phorum 3.0.7 allows remote attackers to access restricted web pages via an HTTP request with the PHP_AUTH_USER parameter set to "boogieman".
Phorum 3.0.7 contains a critical backdoor vulnerability in auth.php3, allowing unauthenticated attackers to bypass authentication and gain unauthorized access to restricted web pages. Successful exploitation grants attackers access with the privileges of the webserver user, potentially leading to data breaches and system compromise.
Step 1: Target Identification: Identify a web server running Phorum 3.0.7.
Step 2: Craft HTTP Request: Construct an HTTP request to a restricted page within the Phorum installation.
Step 3: Set PHP_AUTH_USER: Include the HTTP header PHP_AUTH_USER: boogieman in the request.
Step 4: Send Request: Transmit the crafted HTTP request to the vulnerable server.
Step 5: Authentication Bypass: The auth.php3 script, upon receiving the request, checks the PHP_AUTH_USER header. Because the value is "boogieman", the authentication check is bypassed.
Step 6: Access Granted: The attacker is granted access to the restricted page, effectively bypassing all authentication requirements.
The vulnerability stems from a hardcoded check within auth.php3. The code directly compares the value of the PHP_AUTH_USER HTTP header against the string "boogieman". If a match is found, the authentication check is bypassed, granting access. This bypass is a direct result of insufficient input validation and a lack of proper authentication mechanisms. The flawed logic allows an attacker to bypass the intended security controls without any complex exploitation techniques. The root cause is a simple, easily exploitable backdoor implemented by the developers.
Due to the age of the vulnerability, it's unlikely to be directly associated with specific APT groups. However, any attacker seeking to gain initial access or escalate privileges could leverage this. While not directly listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, the potential for exploitation makes it a high-risk vulnerability. Not in CISA KEV.
Web Server Logs: Examine web server access logs (e.g., Apache, Nginx) for HTTP requests containing the PHP_AUTH_USER: boogieman header. Successful exploitation will result in 200 OK responses to restricted pages.
Intrusion Detection Systems (IDS): Configure IDS rules to detect HTTP requests with the PHP_AUTH_USER: boogieman header.
File Integrity Monitoring: Monitor the auth.php3 file for any unauthorized modifications.
Network Traffic Analysis: Analyze network traffic for HTTP requests targeting the Phorum installation, specifically looking for the PHP_AUTH_USER header.
Upgrade Phorum: Upgrade to a patched version of Phorum that addresses this vulnerability. This is the primary and most effective remediation step.
Remove or Disable auth.php3 (If Possible): If upgrading is not immediately feasible, consider removing or disabling the auth.php3 file if it's not essential for the forum's functionality. This will prevent the backdoor from being triggered.
Implement Web Application Firewall (WAF): Deploy a WAF to filter malicious HTTP requests, including those with the PHP_AUTH_USER: boogieman header.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities proactively.
Monitor Web Server Logs: Continuously monitor web server logs for suspicious activity, including attempts to access restricted pages or unusual HTTP headers.
Patch Management: Implement a robust patch management process to ensure that all software, including Phorum and the underlying web server, is up-to-date with the latest security patches.