CVE-2014-7990 in IOS XE
Summary
by MITRE
Cisco IOS XE 3.5E and earlier on WS-C3850, WS-C3860, and AIR-CT5760 devices does not properly parse the "request system shell" challenge response, which allows local users to obtain Linux root access by leveraging administrative privilege, aka Bug ID CSCur09815.
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Analysis
by VulDB Data Team • 02/24/2022
The vulnerability identified as CVE-2014-7990 represents a critical privilege escalation flaw within Cisco IOS XE software versions 3.5E and earlier that affects multiple network device platforms including the WS-C3850, WS-C3860, and AIR-CT5760 series. This issue stems from improper parsing of the "request system shell" challenge response mechanism, creating a pathway for local attackers to escalate their privileges from administrative level to full root access within the underlying Linux operating system. The vulnerability specifically targets the authentication and authorization processes that govern access to the device's command-line interface and system shell functionality.
The technical flaw manifests in the insufficient validation and processing of challenge-response mechanisms used during system shell access requests. When administrators attempt to access the Linux shell through the IOS XE interface, the system fails to properly validate the response to the challenge prompts, allowing malicious input to bypass security checks. This weakness enables attackers who already possess administrative credentials to exploit the parsing inconsistency and gain root-level access to the underlying Linux kernel and system resources. The vulnerability operates at the intersection of operating system-level privilege management and network device command processing, creating a significant security gap that undermines the device's access control mechanisms.
From an operational perspective, this vulnerability presents a severe risk to network infrastructure security as it allows local attackers to escalate their privileges without requiring additional authentication credentials or exploiting external attack vectors. The impact extends beyond simple privilege escalation since root access provides complete control over the device's operating system, including the ability to modify system files, install malicious software, alter network configurations, and potentially use the compromised device as a pivot point for attacks against other network segments. Network administrators face the challenge of having to patch multiple device models across their infrastructure, as the vulnerability affects several Cisco product lines that may be deployed in critical network positions.
The vulnerability maps directly to CWE-284 (Improper Access Control) and CWE-345 (Insufficient Verification of Data Authenticity) within the Common Weakness Enumeration framework, highlighting the fundamental flaws in access control validation and authentication response processing. From the MITRE ATT&CK framework perspective, this vulnerability aligns with techniques such as privilege escalation and command and control operations, as it enables attackers to establish persistent access to network devices and potentially use them as command centers for broader network infiltration. Organizations must consider this vulnerability as part of their broader security posture assessment, particularly in environments where network device security is paramount.
Mitigation strategies for CVE-2014-7990 require immediate deployment of Cisco's security patches and software updates that address the flawed challenge-response parsing mechanism. Network administrators should implement strict access controls limiting administrative privileges to only essential personnel and establish monitoring procedures to detect unauthorized access attempts. The remediation process involves upgrading affected devices to IOS XE versions that contain proper validation of system shell challenges and response mechanisms. Organizations should also conduct comprehensive vulnerability assessments across their entire network infrastructure to identify any other devices running vulnerable software versions and ensure that all administrative access controls remain properly enforced. Additionally, implementing network segmentation and access control policies can limit the potential impact if devices become compromised.