CVE-2020-3209 in IOS XE
Summary
by MITRE
A vulnerability in software image verification in Cisco IOS XE Software could allow an unauthenticated, physical attacker to install and boot a malicious software image or execute unsigned binaries on an affected device. The vulnerability is due to an improper check on the area of code that manages the verification of the digital signatures of system image files during the initial boot process. An attacker could exploit this vulnerability by loading unsigned software on an affected device. A successful exploit could allow the attacker to install and boot a malicious software image or execute unsigned binaries on the targeted device.
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Analysis
by VulDB Data Team • 10/21/2020
This vulnerability exists within Cisco IOS XE Software's image verification mechanism, representing a critical security flaw that undermines the integrity protection of network infrastructure devices. The issue stems from insufficient validation of digital signatures during the boot process, creating an exploitable condition that allows unauthorized code execution. The vulnerability specifically affects the code area responsible for managing system image file verification, where the signature checking logic fails to properly validate the authenticity of software images. This weakness enables a physical attacker with access to the device to bypass the intended security controls that should prevent installation of untrusted software components.
The technical implementation of this vulnerability demonstrates a failure in the cryptographic verification process that should occur during system initialization. During the boot sequence, the software should validate digital signatures against trusted certificates and ensure that only authorized code can execute. However, the improper check allows attackers to load unsigned binaries or malicious software images that would normally be rejected by the verification system. This flaw operates at a fundamental level of the operating system's security architecture, affecting the core boot process where integrity checks should provide the first line of defense against malicious code execution. The vulnerability's impact is amplified by the fact that it requires only physical access to the device, making it particularly dangerous in environments where physical security controls may be inadequate.
From an operational standpoint, this vulnerability creates significant risk for network infrastructure devices running affected Cisco IOS XE versions. An attacker with physical access could potentially compromise entire network segments by installing backdoor software or malicious firmware that persists across reboots. The exploitation capability extends beyond simple code execution to include full system compromise, as the malicious software would be able to run with system privileges and potentially establish persistent access. This vulnerability directly relates to CWE-320, which addresses cryptographic failures, and aligns with ATT&CK techniques involving privilege escalation and persistence mechanisms. The attack surface is particularly concerning for critical infrastructure devices where physical access might be gained through social engineering, insider threats, or inadequate physical security controls.
Mitigation strategies should focus on immediate software updates and patches provided by Cisco to address the specific signature verification flaw in the boot process. Network administrators should implement strict physical security measures to prevent unauthorized access to network devices, including secure device placement, access controls, and monitoring of physical access points. The remediation process requires careful planning due to the nature of the vulnerability, as updating the software during the boot process may require specific procedures to avoid device lockout. Organizations should also implement additional monitoring capabilities to detect unauthorized software installations or unusual boot patterns that might indicate exploitation attempts. Regular security assessments should verify that physical access controls are adequate and that the updated software properly enforces signature verification during all boot sequences. The vulnerability highlights the importance of maintaining robust integrity verification mechanisms throughout the entire system lifecycle, particularly in critical network infrastructure where unauthorized code execution could have widespread consequences.