CVE-2020-15861 in net-snmp
Summary
by MITRE
Net-SNMP through 5.7.3 allows Escalation of Privileges because of UNIX symbolic link (symlink) following.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2020-15861 affects Net-SNMP versions through 5.7.3 and represents a critical privilege escalation flaw stemming from improper handling of symbolic links within the UNIX filesystem. This issue arises when the Net-SNMP daemon processes configuration files or manages temporary files that may contain symbolic links, creating opportunities for malicious actors to manipulate the system's privilege structure. The vulnerability specifically exploits the lack of proper symlink validation during file operations, allowing attackers to bypass intended access controls and gain elevated system privileges.
The technical root cause of this vulnerability lies in the insufficient validation of symbolic links within the Net-SNMP implementation, which falls under CWE-59. This weakness enables attackers to create or manipulate symbolic links in locations where the daemon expects regular files, thereby redirecting file operations to unintended targets. When the Net-SNMP service processes these manipulated links, it executes operations with elevated privileges, potentially allowing unauthorized users to gain root access or access restricted system resources. The flaw demonstrates a classic path traversal vulnerability where the system fails to properly resolve file paths before performing operations.
The operational impact of CVE-2020-15861 is severe and multifaceted, as it enables attackers to escalate their privileges from standard user accounts to root or administrative levels within systems running vulnerable Net-SNMP versions. This privilege escalation can lead to complete system compromise, data exfiltration, lateral movement within network environments, and persistent backdoor establishment. Organizations using Net-SNMP for network monitoring and management are particularly at risk since the daemon typically runs with elevated privileges to access system information and manage network configurations. The vulnerability can be exploited remotely through SNMP protocol interactions or locally through privilege escalation attacks, making it a significant threat vector for both external attackers and insider threats.
Mitigation strategies for CVE-2020-15861 focus primarily on updating to patched versions of Net-SNMP where the symbolic link handling has been properly addressed. Organizations should immediately upgrade to Net-SNMP version 5.8 or later, which includes fixes for the symlink following vulnerability. Additionally, system administrators should implement proper file permissions and access controls, ensuring that the Net-SNMP daemon runs with minimal required privileges rather than elevated permissions. Network segmentation and firewall rules should be configured to limit SNMP access to trusted sources only, reducing the attack surface. Regular security audits and monitoring for unauthorized symbolic link creation in critical directories should be implemented as part of ongoing security operations. This vulnerability aligns with ATT&CK technique T1068, which covers privilege escalation through local exploits, and demonstrates the importance of proper input validation and file system security controls in preventing unauthorized privilege elevation.