CVE-2017-15700 in Sling
Summary
by MITRE
A flaw in the org.apache.sling.auth.core.AuthUtil#isRedirectValid method in Apache Sling Authentication Service 1.4.0 allows an attacker, through the Sling login form, to trick a victim to send over their credentials.
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Analysis
by VulDB Data Team • 12/15/2019
The vulnerability identified as CVE-2017-15700 resides within the Apache Sling Authentication Service component, specifically in the AuthUtil#isRedirectValid method implementation. This flaw represents a critical security weakness that enables attackers to manipulate the authentication flow through crafted redirects, potentially leading to credential theft. The vulnerability affects Apache Sling versions up to and including 1.4.0, making it a significant concern for organizations relying on this content management framework for their web applications.
The technical implementation flaw stems from insufficient validation of redirect URLs within the authentication service's redirect handling mechanism. When users attempt to log in through the Sling login form, the system processes redirect parameters that determine where users are sent after successful authentication. The isRedirectValid method fails to properly sanitize or validate these redirect URLs, allowing malicious actors to craft URLs that appear legitimate but redirect users to attacker-controlled domains. This validation bypass enables attackers to construct deceptive login pages that mimic the genuine authentication interface while capturing user credentials.
From an operational impact perspective, this vulnerability creates a severe risk for organizations using Apache Sling applications, particularly those with user authentication requirements. Attackers can exploit this weakness through various means including phishing campaigns, social engineering, or by compromising other parts of the application to inject malicious redirect parameters. The vulnerability essentially allows for credential harvesting attacks where users unknowingly submit their credentials to malicious sites that appear to be legitimate authentication endpoints. This type of attack falls under the ATT&CK framework's credential access tactics, specifically targeting the credential dumping and input validation techniques.
The vulnerability's exploitation requires minimal technical sophistication from attackers, making it particularly dangerous in production environments. It can be leveraged to compromise user sessions and potentially escalate privileges within applications that rely on Sling's authentication mechanisms. Organizations should consider this vulnerability in their security posture assessments, as it represents a persistent threat that can be exploited across multiple application contexts where Sling authentication is implemented. The flaw's classification aligns with CWE-601, which addresses URL redirect vulnerabilities and the potential for open redirect attacks that can lead to credential theft.
Mitigation strategies should prioritize immediate patching of affected Apache Sling installations to version 1.4.1 or later, which contains the necessary fixes for the redirect validation logic. Organizations should also implement additional defensive measures such as monitoring for suspicious redirect patterns in authentication logs, implementing strict redirect URL validation policies, and conducting security reviews of authentication flows. Network-level controls including web application firewalls and strict ingress/egress policies can provide additional protection layers. Security teams should also consider implementing user education programs to recognize potential credential harvesting attempts and establish incident response procedures specifically addressing authentication-related security events. The vulnerability demonstrates the importance of proper input validation and the critical need for security reviews of authentication mechanisms in web applications.