CVE-2021-21518 in SupportAssist Client
Summary
by MITRE • 03/13/2021
Dell SupportAssist Client for Consumer PCs versions 3.7.x, 3.6.x, 3.4.x, 3.3.x, Dell SupportAssist Client for Business PCs versions 2.0.x, 2.1.x, 2.2.x, and Dell SupportAssist Client ProManage 1.x contain a DLL injection vulnerability in the Costura Fody plugin. A local user with low privileges could potentially exploit this vulnerability, leading to the execution of arbitrary executable on the operating system with SYSTEM privileges.
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Analysis
by VulDB Data Team • 04/01/2021
The vulnerability identified as CVE-2021-21518 resides within Dell SupportAssist Client software across multiple consumer and business product lines, specifically affecting versions 3.7.x, 3.6.x, 3.4.x, 3.3.x for consumer PCs and 2.0.x, 2.1.x, 2.2.x for business PCs, along with ProManage 1.x. This flaw manifests through the Costura Fody plugin implementation which handles assembly loading and deployment within the application framework. The issue represents a critical security weakness that allows privilege escalation from low-privilege user accounts to SYSTEM level execution capabilities, making it particularly dangerous for enterprise environments where user access controls are paramount.
The technical root cause of this vulnerability stems from insecure dynamic link library loading practices within the Costura Fody plugin component. When the Dell SupportAssist Client application executes, it loads external libraries without proper validation of their authenticity or location, creating an opportunity for malicious actors to inject unauthorized DLL files into the execution path. This behavior directly maps to CWE-426 Untrusted Search Path and CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component, both of which are well-documented weaknesses in software security frameworks. The vulnerability specifically exploits the principle of least privilege by allowing a local attacker to bypass normal access controls and elevate their privileges to the highest system level.
From an operational perspective, this vulnerability presents a significant risk to organizations deploying Dell SupportAssist Client software, as it enables a local attacker with minimal privileges to gain SYSTEM-level access to target machines. The attack vector requires only local system access, making it particularly concerning for environments where user accounts may be compromised through phishing or other social engineering techniques. Once exploited, the attacker gains complete control over the affected system, potentially allowing for data exfiltration, persistence mechanisms installation, or further network reconnaissance activities. This vulnerability directly aligns with ATT&CK technique T1068 Exploitation for Privilege Escalation and T1547.001 Registry Run Keys / Startup Folder, as it provides the initial foothold for system-level compromise.
Mitigation strategies for CVE-2021-21518 should prioritize immediate software updates from Dell to address the vulnerable Costura Fody plugin implementation. Organizations should implement strict application whitelisting policies to prevent unauthorized DLL execution and monitor for suspicious loading patterns of external libraries. Network segmentation and principle of least privilege enforcement can help limit the potential impact of successful exploitation. System administrators should also conduct thorough vulnerability assessments to identify any other applications using the same vulnerable plugin or similar insecure loading patterns. The remediation process must include verification that updated software versions properly address the DLL injection vulnerability through security scanning tools and penetration testing procedures to ensure complete mitigation of the identified threat vector.