CVE-2020-3545 in FXOS
Summary
by MITRE
A vulnerability in Cisco FXOS Software could allow an authenticated, local attacker with administrative credentials to cause a buffer overflow condition. The vulnerability is due to incorrect bounds checking of values that are parsed from a specific file. An attacker could exploit this vulnerability by supplying a crafted file that, when it is processed, may cause a stack-based buffer overflow. A successful exploit could allow the attacker to execute arbitrary code on the underlying operating system with root privileges. An attacker would need to have valid administrative credentials to exploit this vulnerability.
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Analysis
by VulDB Data Team • 11/12/2020
The vulnerability identified as CVE-2020-3545 represents a critical buffer overflow flaw within Cisco FXOS Software, a foundational component of Cisco's fabric extensibility operating system that manages network infrastructure devices. This security weakness resides in the software's handling of file parsing operations, specifically where improper bounds checking occurs when processing certain input data structures. The vulnerability's exploitation requires an attacker to possess valid administrative credentials, establishing it as a local privilege escalation issue rather than a remote attack vector. The flaw manifests when the system processes a specially crafted file that contains malformed data structures, triggering a stack-based buffer overflow condition that can be leveraged for arbitrary code execution.
The technical implementation of this vulnerability stems from insufficient input validation mechanisms within the FXOS software's file processing pipeline. When the system attempts to parse values from a specific file format, it fails to properly validate the boundaries of memory allocations, allowing an attacker to overflow buffer space allocated on the stack. This type of vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of improper input validation that enables attackers to overwrite adjacent memory locations. The buffer overflow occurs during the parsing phase of file processing, where the software does not adequately check the length or content of input data before copying it into fixed-size buffers. The attack vector specifically targets the administrative interface of the FXOS software, requiring the attacker to have already established administrative access to the system, which reduces the attack surface but does not eliminate the severity of the potential exploitation.
The operational impact of this vulnerability extends beyond simple privilege escalation, as successful exploitation provides attackers with complete root-level access to the underlying operating system. This elevated privilege level enables unauthorized users to execute arbitrary code, modify system configurations, access sensitive data, and potentially establish persistent backdoors within the network infrastructure. The implications for network security are particularly severe given that FXOS Software operates at the core of Cisco's fabric extensibility platform, managing critical network functions and device communications. Attackers could leverage this vulnerability to gain complete control over network devices, potentially disrupting network operations, stealing confidential information, or using the compromised systems as launch points for further attacks within the network infrastructure. The vulnerability's classification under the ATT&CK framework would fall under privilege escalation techniques, specifically targeting local privilege escalation methods that exploit software vulnerabilities to gain administrative access.
Mitigation strategies for CVE-2020-3545 should focus on both immediate remediation and long-term security enhancements. Cisco has released patches and software updates to address this vulnerability, which should be deployed immediately across all affected systems. Organizations should implement strict access control measures to limit administrative credentials and ensure that only authorized personnel have access to administrative functions. Network segmentation and monitoring systems should be enhanced to detect unusual file processing activities that might indicate exploitation attempts. Additionally, regular security assessments and vulnerability scanning should be conducted to identify similar issues within the FXOS software environment. The implementation of principle of least privilege should be enforced, ensuring that administrative accounts have minimal necessary permissions and that file processing operations are properly validated before execution. Security teams should also consider implementing application whitelisting controls to prevent unauthorized file execution and establish monitoring protocols that can detect buffer overflow exploitation attempts. Organizations should maintain detailed audit logs of administrative activities and file processing operations to enable rapid incident response and forensic analysis in case of successful exploitation attempts.