CVE-2016-6496 in Crowd
Summary
by MITRE
The LDAP directory connector in Atlassian Crowd before 2.8.8 and 2.9.x before 2.9.5 allows remote attackers to execute arbitrary code via an LDAP attribute with a crafted serialized Java object, aka LDAP entry poisoning.
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Analysis
by VulDB Data Team • 05/21/2019
The vulnerability identified as CVE-2016-6496 represents a critical remote code execution flaw within Atlassian Crowd's LDAP directory connector component. This vulnerability exists in versions prior to 2.8.8 and 2.9.x versions before 2.9.5, creating a significant security risk for organizations relying on Crowd for identity management and authentication services. The flaw stems from insufficient input validation and sanitization of LDAP attributes, particularly when processing serialized Java objects within directory entries. Attackers can exploit this weakness by crafting malicious LDAP entries containing specially constructed serialized Java objects that, when processed by the vulnerable Crowd application, trigger arbitrary code execution on the target system.
The technical exploitation of this vulnerability involves leveraging the Java deserialization mechanism within the LDAP connector to execute malicious code with the privileges of the Crowd application. When Crowd processes LDAP directory entries containing crafted serialized objects, the application's deserialization process fails to properly validate or sanitize the input, allowing attackers to inject malicious code that gets executed during the LDAP attribute processing phase. This vulnerability specifically targets the deserialization of Java objects within LDAP attributes, making it a variant of deserialization vulnerabilities that are commonly exploited in enterprise applications. The flaw enables attackers to perform remote code execution without requiring authentication, as the vulnerability exists within the LDAP processing functionality that typically operates independently of user authentication.
The operational impact of CVE-2016-6496 is severe and far-reaching for organizations using vulnerable versions of Atlassian Crowd. Successful exploitation can result in complete system compromise, allowing attackers to gain unauthorized access to sensitive user data, modify authentication records, and potentially establish persistent backdoors within the network. The vulnerability affects the core identity management infrastructure, which often serves as a central point of access for multiple applications and services, amplifying the potential damage. Organizations may experience data breaches, service disruptions, and compliance violations due to the unauthorized access and execution capabilities provided by this vulnerability. The impact extends beyond immediate system compromise to include potential lateral movement within the network and escalation of privileges to administrative levels.
Organizations should immediately implement mitigations including updating to the patched versions of Atlassian Crowd 2.8.8 and 2.9.5 or later, which contain proper input validation and sanitization for LDAP attributes. Security teams should also consider implementing network-level restrictions to limit LDAP traffic to trusted sources and monitor for suspicious LDAP attribute patterns. The vulnerability aligns with CWE-502, which describes deserialization of untrusted data, and maps to attack techniques in the ATT&CK framework under T1059.007 for scripting and T1133 for external remote services. Additionally, organizations should review their LDAP configurations and implement proper access controls to minimize the attack surface. The remediation process should include thorough testing of the patched versions in staging environments to ensure compatibility with existing LDAP configurations and user authentication workflows.