CVE-2015-2750 in Drupal
Summary
by MITRE
Open redirect vulnerability in URL-related API functions in Drupal 6.x before 6.35 and 7.x before 7.35 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via vectors involving the "//" initial sequence.
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Analysis
by VulDB Data Team • 01/12/2021
The vulnerability identified as CVE-2015-2750 represents a critical open redirect flaw affecting Drupal content management systems across multiple versions. This security weakness resides within the URL-related application programming interface functions of Drupal 6.x systems prior to version 6.35 and Drupal 7.x systems prior to version 7.35. The flaw specifically exploits how the system processes URLs that begin with the double forward slash sequence "//" which creates a dangerous pathway for malicious redirection attacks. The vulnerability classification aligns with CWE-601 Open Redirect, which is categorized under the broader category of input validation and injection flaws in the CWE top 25 most dangerous software weaknesses. This weakness allows attackers to manipulate URL handling mechanisms to redirect users to malicious websites while maintaining the appearance of legitimate Drupal functionality.
The technical implementation of this vulnerability occurs when Drupal processes URLs that contain the double slash prefix, which bypasses normal URL validation checks and allows attackers to craft malicious links that appear to originate from the legitimate Drupal domain. When users click on these specially crafted links, they are transparently redirected to attacker-controlled websites without any warning to the end user. The flaw exploits the underlying assumption that URLs beginning with "//" should be treated as relative paths and allows attackers to leverage this behavior to create phishing campaigns that appear legitimate to users. This mechanism particularly affects the redirect functionality within Drupal's core URL handling system, where the system fails to properly validate and sanitize URLs before executing redirects. The vulnerability demonstrates a clear breakdown in the principle of least privilege and proper input sanitization, as the system does not adequately verify the destination of redirects before executing them.
The operational impact of CVE-2015-2750 extends far beyond simple redirection capabilities and creates significant security risks for organizations running affected Drupal installations. Attackers can leverage this vulnerability to conduct sophisticated phishing campaigns where users are redirected to malicious sites that mimic legitimate Drupal interfaces, enabling credential theft and other malicious activities. The open redirect vulnerability allows attackers to bypass security measures such as URL filtering and browser warnings that typically protect users from malicious redirections. Organizations using affected Drupal versions face potential data breaches, reputation damage, and regulatory compliance issues when users are unknowingly redirected to phishing sites. The vulnerability also enables attackers to perform social engineering campaigns that exploit user trust in the legitimate Drupal platform, making the attack vectors more effective and harder to detect. This type of vulnerability is particularly dangerous in enterprise environments where Drupal is used for public-facing websites, portals, and applications that handle sensitive user data.
The mitigation strategy for CVE-2015-2750 requires immediate patching of affected Drupal installations to the recommended versions that contain the security fixes. Organizations should upgrade to Drupal 6.35 or later for version 6.x installations and Drupal 7.35 or later for version 7.x installations. Additionally, administrators should implement URL validation checks at the application level to prevent the processing of URLs beginning with double slashes and should monitor web server logs for suspicious redirect patterns. Network security controls including web application firewalls and URL filtering systems should be configured to block known malicious redirect patterns. The vulnerability also highlights the importance of implementing proper input validation and output encoding practices, which aligns with the recommendations in the OWASP Top Ten and the NIST Cybersecurity Framework. Security teams should conduct thorough vulnerability assessments to identify any other instances of similar weaknesses in the application code and ensure that all URL handling functions properly validate and sanitize user-provided input. The remediation process should include comprehensive testing to ensure that the patch does not introduce regressions in legitimate redirect functionality while effectively blocking the malicious redirect vectors.