CVE-2018-15374 in IOS XE
Summary
by MITRE
A vulnerability in the Image Verification feature of Cisco IOS XE Software could allow an authenticated, local attacker to install a malicious software image or file on an affected device. The vulnerability is due to the affected software improperly verifying digital signatures for software images and files that are uploaded to a device. An attacker could exploit this vulnerability by uploading a malicious software image or file to an affected device. A successful exploit could allow the attacker to bypass digital signature verification checks for software images and files and install a malicious software image or file on the affected device.
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Analysis
by VulDB Data Team • 03/30/2020
The vulnerability identified as CVE-2018-15374 resides within the Image Verification feature of Cisco IOS XE Software, representing a critical security flaw that undermines the integrity protection mechanisms designed to safeguard network infrastructure devices. This weakness specifically targets the digital signature verification process that is fundamental to ensuring software authenticity and preventing unauthorized modifications to system images. The vulnerability affects Cisco IOS XE Software versions prior to 16.6.1, making it a widespread concern across numerous network devices that rely on this operating system for their core functionality. The flaw operates at the software validation layer where cryptographic verification processes fail to properly authenticate the integrity of uploaded software images, creating an exploitable condition that compromises the device's security posture.
The technical nature of this vulnerability stems from improper implementation of digital signature verification protocols within the software image handling subsystem of Cisco IOS XE. When an attacker successfully authenticates to the device through legitimate means, they can exploit this weakness to upload malicious software images without triggering the expected signature validation checks. This occurs because the system fails to properly validate the cryptographic signatures associated with the software packages being installed, allowing attackers to bypass the security controls that are meant to ensure only trusted software can be executed on the device. The vulnerability essentially creates a backdoor mechanism that circumvents the intended security architecture by exploiting a flaw in the verification logic that should prevent installation of unauthenticated software components.
From an operational impact perspective, this vulnerability presents a severe threat to network security infrastructure as it allows authenticated local attackers to gain persistent control over affected devices. The successful exploitation enables attackers to install malicious software images that could include backdoors, rootkits, or other malicious components designed to maintain long-term access to the compromised network. This capability fundamentally undermines the device's ability to serve as a secure network component, potentially allowing attackers to establish persistent footholds within the network infrastructure. The vulnerability's impact extends beyond individual device compromise to potentially affect entire network segments if multiple devices are vulnerable, as attackers could use compromised devices as launching points for further network infiltration activities.
The attack vector for this vulnerability requires an authenticated local session on the affected device, which means that an attacker must first obtain valid credentials to exploit the flaw. This requirement significantly reduces the attack surface compared to remote exploits but does not eliminate the risk entirely, as credential compromise can occur through various means including phishing attacks, password reuse, or insider threats. The exploitation process involves uploading a malicious software image that bypasses the digital signature verification mechanism, allowing the attacker to install unauthorized software that could include network monitoring tools, data exfiltration capabilities, or other malicious payloads. This attack pattern aligns with the ATT&CK framework's concept of "Persistence" and "Privilege Escalation" techniques, where attackers establish long-term access and maintain control over compromised systems.
Organizations should implement immediate mitigations including upgrading to Cisco IOS XE Software version 16.6.1 or later, which contains the necessary patches to address the digital signature verification flaw. Network administrators should also enforce strict access controls and monitoring of device authentication activities to detect potential unauthorized access attempts. Additional defensive measures include implementing network segmentation to limit the impact of device compromise, regular security audits of network infrastructure, and maintaining comprehensive backup and recovery procedures for affected devices. The vulnerability demonstrates the critical importance of proper cryptographic implementation and the potential consequences of inadequate software validation mechanisms in network security systems. This flaw serves as a reminder of the essential role that digital signature verification plays in maintaining software integrity and the need for rigorous security testing of all system components that handle software installation and execution processes.