CVE-2019-1813 in NX-OS
Summary
by MITRE
A vulnerability in the Image Signature Verification feature of Cisco NX-OS Software could allow an authenticated, local attacker with administrator-level credentials to install a malicious software image on an affected device. The vulnerability exists because software digital signatures are not properly verified during CLI command execution. An attacker could exploit this vulnerability to install an unsigned software image on an affected device.
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability identified as CVE-2019-1813 resides within the Image Signature Verification functionality of Cisco NX-OS Software, representing a critical security flaw that undermines the integrity protection mechanisms of network infrastructure devices. This weakness specifically affects Cisco Nexus series switches and routers that operate on NX-OS software, where the system fails to properly validate digital signatures during the execution of command line interface operations. The vulnerability is particularly concerning because it requires only authenticated access with administrator-level privileges, making it exploitable by insiders or attackers who have already gained administrative access to the device. The flaw stems from inadequate implementation of cryptographic verification processes that should ensure only legitimate, signed software images can be installed on the system.
The technical nature of this vulnerability aligns with CWE-327, which addresses the use of weak cryptographic algorithms, and more specifically with CWE-328, concerning the use of weak hashing algorithms in digital signatures. The vulnerability operates at the software installation layer where the system should perform cryptographic verification before accepting and installing new software images. When an authenticated administrator executes CLI commands to install software, the system fails to properly validate the digital signature associated with the software image, allowing malicious code to be installed without proper verification. This represents a breakdown in the principle of least privilege and code integrity verification that should be maintained throughout the software lifecycle. The vulnerability is classified under the ATT&CK technique T1547.001, which covers registry run keys and startup folder, as it enables persistent malicious software installation on network devices that could be used to maintain access or escalate privileges.
The operational impact of this vulnerability extends beyond simple software installation, as it fundamentally compromises the security posture of network infrastructure devices that are critical to enterprise and service provider networks. An attacker with administrative credentials could potentially install backdoor software, rootkits, or other malicious components that could persist across device reboots and remain undetected for extended periods. This capability significantly increases the risk of data exfiltration, network disruption, and lateral movement within the affected network environment. The vulnerability affects all Cisco Nexus devices running vulnerable versions of NX-OS software, including but not limited to Nexus 3000, 5000, 6000, 7000, and 9000 series switches. The exploitation requires minimal additional privileges beyond existing administrative access, making it particularly dangerous in environments where administrative accounts may be compromised through social engineering, credential theft, or other attack vectors.
Mitigation strategies for CVE-2019-1813 should prioritize immediate patching of affected devices with the latest Cisco security updates that properly implement digital signature verification. Organizations should also implement strict access controls and monitoring of administrative activities, including logging and alerting on software installation commands executed through the CLI. Network segmentation and privilege separation can help reduce the attack surface by limiting the number of administrators with full administrative privileges. Additionally, implementing robust software supply chain security measures and maintaining detailed inventories of all software images and their cryptographic signatures can help detect unauthorized modifications. The vulnerability highlights the importance of maintaining proper code integrity verification throughout the software lifecycle and emphasizes the need for continuous security testing and validation of cryptographic implementations in network infrastructure devices. Security teams should also consider implementing endpoint detection and response solutions specifically designed for network devices to monitor for suspicious software installation activities and potential exploitation attempts.