Source: cve@mitre.org
violation.php3 in Phorum 3.0.7 allows remote attackers to send e-mails to arbitrary addresses and possibly use Phorum as a "spam proxy" by setting the Mod and ForumName parameters.
Phorum 3.0.7 is vulnerable to a critical flaw in violation.php3 that allows remote attackers to leverage the platform as a spam proxy, enabling the sending of unsolicited emails to arbitrary recipients. This vulnerability could lead to reputational damage, denial-of-service, and potential legal ramifications due to the misuse of the platform for malicious activities.
Step 1: Craft Malicious Request: The attacker constructs a specially crafted HTTP request targeting violation.php3. This request includes the Mod and ForumName parameters, which are used to control the email sending functionality.
Step 2: Parameter Injection: The attacker sets the Mod parameter to a value that will be used as the sender's email address (or a forged sender address). The ForumName parameter is set to the recipient's email address.
Step 3: Email Delivery: The violation.php3 script processes the request, taking the attacker-controlled Mod and ForumName parameters and uses them to construct and send an email. The script does not validate the sender or recipient addresses.
Step 4: Spam Proxy: The Phorum server, acting as a spam proxy, sends the email to the specified recipient, effectively relaying the attacker's message.
The vulnerability stems from a lack of proper input validation and sanitization within the violation.php3 script, specifically concerning the Mod and ForumName parameters. The script fails to adequately verify the origin or intended use of these parameters, allowing attackers to inject arbitrary email addresses into the email sending process. This bypasses any intended restrictions on email sending, effectively turning the Phorum instance into an open relay. The root cause is a missing check on the sender and recipient addresses, and lack of rate limiting or other anti-spam measures. This allows attackers to craft malicious requests that utilize the vulnerable server to send spam emails.
While no specific APTs are directly tied to this vulnerability, any threat actor seeking to distribute spam or launch phishing campaigns could exploit it. This vulnerability is not listed on the CISA KEV list due to its age and the likely low number of actively maintained Phorum 3.0.7 instances.
Monitor web server logs for suspicious POST requests to violation.php3 with unusual Mod and ForumName parameter values.
Analyze network traffic for SMTP connections originating from the Phorum server to external recipients, especially if the sender address appears forged or suspicious.
Implement intrusion detection system (IDS) rules to detect malicious HTTP requests targeting the vulnerable script.
Examine email headers for emails originating from the Phorum server, looking for signs of spam or phishing, and correlate with web server logs.
Upgrade to the latest version of Phorum or a supported version that addresses this vulnerability. If upgrading is not immediately possible, apply the vendor's security patches or workarounds.
Implement input validation and sanitization on all user-supplied data, especially the Mod and ForumName parameters. Specifically, validate email addresses using regular expressions or dedicated email validation functions.
Restrict access to violation.php3 using .htaccess or similar mechanisms, if the functionality is not required.
Implement rate limiting to prevent excessive email sending from the server.
Configure the mail server to reject emails from unauthorized senders and implement SPF, DKIM, and DMARC records to improve email deliverability and reduce the risk of spoofing.
Regularly scan the server for known vulnerabilities and apply security updates promptly.