CVE-2016-2512 in Django
Summary
by MITRE
The utils.http.is_safe_url function in Django before 1.8.10 and 1.9.x before 1.9.3 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks or possibly conduct cross-site scripting (XSS) attacks via a URL containing basic authentication, as demonstrated by http://mysite.example.com\@attacker.com.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability described in CVE-2016-2512 represents a critical security flaw in the Django web framework that affects versions prior to 1.8.10 and 1.9.3. This issue resides within the utils.http.is_safe_url function which is responsible for validating whether URLs are safe for redirection purposes. The flaw enables attackers to craft malicious URLs that appear legitimate but actually redirect users to attacker-controlled domains, creating significant risks for web applications built on Django. The vulnerability specifically exploits how the function handles URLs containing basic authentication credentials, where the authentication portion of the URL can be manipulated to include malicious domain information.
The technical implementation of this vulnerability stems from improper parsing of URLs that contain basic authentication information. When a URL such as http://mysite.example.com\@attacker.com is processed, the function fails to properly separate the authentication credentials from the actual domain portion of the URL. This parsing error allows the attacker to inject a different domain name within the URL structure itself, effectively bypassing the normal URL validation mechanisms that are designed to prevent open redirect vulnerabilities. The flaw specifically manifests when the backslash character is used to separate the authentication information from the host, creating a situation where the URL parser incorrectly interprets the domain component.
The operational impact of this vulnerability extends beyond simple redirection attacks to encompass serious security implications including phishing campaigns and potential cross-site scripting exploitation. Attackers can leverage this vulnerability to create convincing phishing pages that appear to originate from legitimate domains, tricking users into revealing sensitive information or credentials. The vulnerability is particularly dangerous because it can be exploited without requiring any special privileges or complex attack vectors, making it accessible to attackers with minimal technical expertise. Additionally, the potential for XSS exploitation arises when the malformed URL is processed in contexts where user input is not properly sanitized, allowing attackers to inject malicious scripts into web pages.
Organizations using affected Django versions should immediately implement mitigations including updating to patched versions 1.8.10 or 1.9.3, which contain proper URL parsing and validation logic. Security teams should also consider implementing additional URL validation at the application level, particularly for any user-provided redirect parameters. The vulnerability aligns with CWE-601 Open Redirect vulnerability classification and maps to ATT&CK technique T1566.001 Phishing, as it enables the creation of convincing phishing attacks through manipulated URL redirection. Organizations should also review their application code for any custom URL validation logic that might be susceptible to similar parsing issues, as this vulnerability demonstrates the importance of robust input validation and proper URL handling in web applications.