CVE-2021-36724 in SecureConnector
Summary
by MITRE • 12/29/2021
ForeScout - SecureConnector Local Service DoS - A low privilaged user which doesn't have permissions to shutdown the secure connector service writes a large amount of characters in the installationPath. This will cause the buffer to overflow and override the stack cookie causing the service to crash.
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Analysis
by VulDB Data Team • 12/31/2021
The vulnerability identified as CVE-2021-36724 affects ForeScout SecureConnector Local Service, representing a classic buffer overflow condition that can be exploited by low privileged users to achieve denial of service. This issue stems from inadequate input validation within the service's handling of installation path parameters, where the system fails to properly sanitize or limit the length of user-provided data. The flaw specifically manifests when a user without administrative privileges attempts to write an excessive amount of character data to the installation path, creating a scenario where the buffer allocated for this operation exceeds its designated limits. The technical implementation of this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations including stack canaries that are designed to detect such violations.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a significant security weakness in the service's defensive architecture. When the buffer overflow occurs and the stack cookie is overridden, the service crashes and becomes unavailable to legitimate users, effectively creating a denial of service condition that can be triggered by any user with basic access permissions. This makes the vulnerability particularly concerning from a security perspective since it can be exploited by users who should not possess the ability to disrupt system operations. The exploit requires minimal privileges and can be executed through simple file system manipulation or command line operations that write excessive data to the installation path, making it accessible to a broad range of potential attackers. The service's failure to implement proper input sanitization creates a direct pathway for memory corruption that bypasses normal access control mechanisms.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network disruption through resource exhaustion and denial of service attacks. The vulnerability can be leveraged in broader attack chains where initial access might be gained through other means, and this weakness provides a method for attackers to escalate their impact by causing service unavailability. The implementation of proper input validation and bounds checking would address this issue by ensuring that the installation path parameter is properly constrained before processing, preventing the overflow condition from occurring. Security controls should focus on implementing strict input validation at multiple levels including application-level sanitization, system-level resource limits, and monitoring for unusual file system write patterns that might indicate exploitation attempts. Organizations should consider implementing additional logging and alerting mechanisms around service stability and resource usage patterns to detect potential exploitation attempts before they result in complete service disruption.
The root cause of this vulnerability demonstrates poor defensive programming practices that violate fundamental security principles. The service architecture fails to implement proper error handling and input validation mechanisms that would prevent the overflow condition from occurring, creating a situation where user-controlled input can directly corrupt the service's execution environment. This type of vulnerability is particularly dangerous because it can be exploited repeatedly without requiring special privileges or sophisticated techniques, making it a reliable method for attackers to cause persistent service disruption. The lack of proper stack canary validation and memory protection mechanisms in the service implementation creates multiple opportunities for exploitation and highlights the need for comprehensive security testing and code review processes to identify similar conditions in other system components.