CVE-2019-1809 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 patch on an affected device. The vulnerability is due to improper verification of digital signatures for patch images. An attacker could exploit this vulnerability by crafting an unsigned software patch to bypass signature checks and loading it on an affected device. A successful exploit could allow the attacker to boot a malicious software patch image.
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Analysis
by VulDB Data Team • 09/21/2023
The vulnerability identified as CVE-2019-1809 resides within the Image Signature Verification mechanism of Cisco NX-OS Software, representing a critical security flaw that undermines the integrity protection measures designed to safeguard network infrastructure devices. This weakness specifically affects Cisco Nexus series switches and routers running affected software versions, where the system's digital signature validation process fails to properly authenticate patch images, creating an exploitable gap in the device's security posture.
The technical flaw manifests in the improper verification of digital signatures for software patches, where the NX-OS software fails to adequately validate the authenticity and integrity of patch images before installation. This vulnerability stems from insufficient cryptographic validation routines that allow an authenticated attacker with administrator-level privileges to craft and execute unsigned patch files that bypass the signature verification checks. The flaw operates at the software validation layer, where the system's trust model is compromised through inadequate signature validation logic that permits malicious code execution under the guise of legitimate software updates.
Operationally, this vulnerability presents a severe threat landscape where a malicious actor with administrative access can escalate their privileges and compromise the device's integrity by installing unauthorized software patches. The successful exploitation enables attackers to boot malicious software patch images that can persist across device reboots, potentially providing persistent access to the network infrastructure. This capability allows for advanced persistent threats that can manipulate network traffic, disable security features, or establish backdoors for continued unauthorized access, making it particularly dangerous for enterprise network environments where these devices serve as critical infrastructure components.
The vulnerability aligns with CWE-330 Use of Insufficiently Random Values and CWE-347 Improper Verification of Cryptographic Signature, demonstrating weaknesses in both the randomness of signature validation processes and the cryptographic verification mechanisms. From an ATT&CK framework perspective, this vulnerability maps to T1068 Exploitation for Privilege Escalation and T1547.001 Registry Run Keys / Startup Folder, as it allows for privilege escalation through patch installation and can enable persistence mechanisms. Organizations should implement immediate mitigations including applying Cisco's security patches, implementing strict access controls for administrative accounts, and monitoring for unauthorized patch installations. Additional protective measures include enabling secure boot processes, implementing network segmentation, and conducting regular security audits to detect potential exploitation attempts, as the vulnerability fundamentally compromises the integrity of the device's software update mechanism and could lead to complete system compromise.