Source: cve@mitre.org
Open redirect vulnerability in forum/login.php in vBulletin 4.1.3 and earlier allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via the url parameter in a lostpw action.
vBulletin 4.1.3 and earlier are vulnerable to an open redirect vulnerability, allowing attackers to manipulate the url parameter in the lostpw action to redirect users to malicious websites. This flaw enables phishing attacks and potential credential theft, posing a significant risk to user accounts and organizational security.
Step 1: Crafting the Malicious URL: The attacker constructs a malicious URL targeting the vulnerable vBulletin installation. The URL includes the forum/login.php script with the lostpw action and a crafted url parameter.
Step 2: Payload Delivery: The attacker distributes the malicious URL through various channels, such as phishing emails, social media posts, or compromised websites.
Step 3: User Interaction: A user clicks on the malicious URL, typically believing it's a legitimate link related to the vBulletin forum.
Step 4: Server-Side Processing: The vBulletin server receives the request and processes the lostpw action. It attempts to redirect the user to the URL specified in the url parameter.
Step 5: Redirection to Malicious Site: Due to the lack of proper validation, the server redirects the user to the attacker-controlled website specified in the url parameter. This site can then be used for phishing, malware distribution, or other malicious activities.
The vulnerability stems from insufficient input validation and sanitization of the url parameter within the forum/login.php script. Specifically, the script fails to properly validate the destination URL provided by the user when handling the 'lostpw' action. This allows an attacker to inject a malicious URL into the url parameter, which is then used in a redirect, leading the user to a phishing site or other malicious content. The root cause is a lack of proper URL validation and sanitization, allowing for arbitrary redirection. This is a classic example of an open redirect vulnerability, which can be easily exploited due to the script's trust in the user-supplied input.
While no specific APT groups are directly linked to this CVE, open redirect vulnerabilities are commonly used by various threat actors for phishing and credential harvesting. The ease of exploitation makes it a favorite among less sophisticated attackers as well. Not listed on CISA KEV.
Monitor web server logs for unusual HTTP redirects originating from forum/login.php with the lostpw action and a suspicious url parameter.
Analyze network traffic for HTTP requests containing the vulnerable URL pattern (e.g., forum/login.php?do=lostpw&url=...).
Implement a web application firewall (WAF) rule to detect and block requests containing suspicious URLs that could be used for open redirection.
Monitor for phishing emails that contain links to the vulnerable vBulletin installation.
Upgrade to a patched version of vBulletin (4.1.4 or later).
Implement input validation and sanitization on the url parameter to ensure it points to a trusted domain.
Use a regular expression or a whitelist approach to validate the URL.
Implement output encoding to prevent cross-site scripting (XSS) vulnerabilities if user-supplied data is displayed.
Configure a Content Security Policy (CSP) to restrict the sources from which the browser can load resources, mitigating the impact of successful exploitation.