CVE-2019-1732 in NX-OS
Summary
by MITRE
A vulnerability in the Remote Package Manager (RPM) subsystem of Cisco NX-OS Software could allow an authenticated, local attacker with administrator credentials to leverage a time-of-check, time-of-use (TOCTOU) race condition to corrupt local variables, which could lead to arbitrary command injection. The vulnerability is due to the lack of a proper locking mechanism on critical variables that need to stay static until used. An attacker could exploit this vulnerability by authenticating to an affected device and issuing a set of RPM-related CLI commands. A successful exploit could allow the attacker to perform arbitrary command injection. The attacker would need administrator credentials for the targeted device.
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Analysis
by VulDB Data Team • 09/19/2023
The vulnerability identified as CVE-2019-1732 represents a critical time-of-check, time-of-use race condition within Cisco NX-OS Software's Remote Package Manager subsystem. This flaw exists in the authentication and authorization mechanisms of network infrastructure devices, specifically targeting the RPM functionality that manages software packages on Cisco Nexus switches and routers. The vulnerability is particularly concerning because it requires only local administrator credentials to exploit, making it accessible to attackers who have already gained administrative access to the device through other means. The TOCTOU race condition manifests when the system checks a variable's state at one point in time and then uses that same variable at a later point, creating an opportunity for manipulation between these two critical moments.
The technical implementation of this vulnerability stems from inadequate synchronization mechanisms within the RPM subsystem's code execution flow. When administrative users execute RPM-related commands, the system fails to implement proper locking mechanisms around critical variables that must maintain their static state throughout the entire execution cycle. This design flaw allows an attacker to manipulate these variables between the check and use phases, effectively corrupting local variables that control command execution paths. The vulnerability specifically affects the handling of package management operations where the system's internal state variables are not properly protected against concurrent modification during command processing. This weakness creates a window of opportunity where an attacker can inject malicious commands that will execute with the privileges of the administrative session.
The operational impact of CVE-2019-1732 extends beyond simple command injection, as it provides attackers with a persistent foothold within network infrastructure devices. Once exploited, the vulnerability allows attackers to execute arbitrary commands on the affected device with full administrative privileges, potentially enabling them to modify network configurations, install malicious software, or establish backdoors for continued access. The attack vector requires only local access with administrator credentials, which means that attackers who have already compromised administrative accounts or gained physical access to the device can leverage this vulnerability to escalate their privileges or perform unauthorized operations. This makes the vulnerability particularly dangerous in environments where administrative credentials might be compromised through other attack vectors, such as credential theft or social engineering. The impact is further amplified because network infrastructure devices often serve as critical points in enterprise networks, making successful exploitation potentially devastating to overall network security posture.
Security mitigations for CVE-2019-1732 should focus on implementing proper locking mechanisms around critical variables within the RPM subsystem and ensuring that all state variables remain static during command execution. Cisco has released patches and software updates that address this vulnerability by introducing proper synchronization controls and race condition protections. Organizations should immediately apply these patches to all affected Cisco NX-OS devices and implement monitoring for suspicious administrative activities. Additionally, network security teams should consider implementing least privilege principles for administrative access, ensuring that only necessary personnel have administrative credentials, and establishing robust audit trails for all RPM-related commands. The vulnerability aligns with CWE-362, which specifically addresses race conditions in concurrent programming, and represents a classic example of how inadequate synchronization can lead to privilege escalation and arbitrary code execution in network infrastructure devices. From an ATT&CK perspective, this vulnerability maps to privilege escalation and command and control techniques, as it enables attackers to execute arbitrary commands with elevated privileges on network devices.