CVE-2013-6943 in NetScaler
Summary
by MITRE
Citrix NetScaler Application Delivery Controller (ADC) 9.3.x before 9.3-64.4, 10.0 before 10.0-77.5, and 10.1 before 10.1-118.7 allows remote attackers to conduct an LDAP injection attack via vectors related to SSH and Web management usernames.
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Analysis
by VulDB Data Team • 05/07/2026
The Citrix NetScaler Application Delivery Controller represents a critical infrastructure component widely deployed for load balancing, application delivery, and security services in enterprise environments. This vulnerability affects specific versions of the NetScaler ADC platform, creating a significant security risk that could be exploited by remote attackers. The affected versions include 9.3.x prior to 9.3-64.4, 10.0 prior to 10.0-77.5, and 10.1 prior to 10.1-118.7, indicating a substantial attack surface across multiple major releases. The vulnerability stems from improper input validation mechanisms within the authentication subsystem, specifically when processing usernames submitted through SSH and web management interfaces.
The technical flaw manifests as an LDAP injection vulnerability that occurs when user-supplied input containing special LDAP characters is not properly sanitized or escaped before being incorporated into LDAP queries. This injection occurs during the authentication process when administrators or users submit usernames through SSH or web management interfaces. The vulnerability enables attackers to manipulate LDAP queries by injecting malicious LDAP filter syntax, potentially allowing them to bypass authentication mechanisms, access unauthorized administrative functions, or extract sensitive directory information from the underlying LDAP directory service. The flaw is particularly dangerous because it affects both SSH and web management interfaces, providing multiple attack vectors for exploitation.
The operational impact of this vulnerability extends beyond simple authentication bypasses and could enable comprehensive compromise of the NetScaler appliance. Attackers could leverage this vulnerability to gain administrative access to the appliance, potentially leading to complete control over load balancing configurations, SSL offloading settings, and application delivery policies. The attack could result in service disruption, data interception, or lateral movement within the network if the compromised appliance serves as a gateway to other systems. The vulnerability also poses risks to the underlying LDAP directory service, as successful injection attacks could reveal directory structure information, user accounts, or other sensitive data. Organizations using these vulnerable versions face significant risk of unauthorized access to critical application delivery infrastructure.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems to the latest available versions that contain the necessary security fixes. Organizations should implement network segmentation to limit access to NetScaler appliances, restrict SSH and web management access to trusted IP addresses, and enforce strong authentication mechanisms including multi-factor authentication. The remediation process should include comprehensive network monitoring to detect potential exploitation attempts and regular security assessments of the appliance configuration. Security teams should also implement proper input validation controls at multiple layers of the application stack, including the LDAP query construction process, to prevent similar injection vulnerabilities from occurring in other components. This vulnerability aligns with CWE-94, which describes improper control of generation of code, and maps to ATT&CK technique T1110.003 for credential access through brute force or credential stuffing attacks, highlighting the critical nature of proper input sanitization and authentication controls in maintaining system security.