CVE-2000-0506 in Linux
Summary
by MITRE
The "capabilities" feature in Linux before 2.2.16 allows local users to cause a denial of service or gain privileges by setting the capabilities to prevent a setuid program from dropping privileges, aka the "Linux kernel setuid/setcap vulnerability."
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Analysis
by VulDB Data Team • 11/27/2024
The vulnerability described in CVE-2000-0506 represents a critical flaw in the Linux kernel's capability implementation that existed prior to version 2.2.16. This issue specifically targets the interaction between the kernel's capability system and setuid programs, creating a pathway for local attackers to either disrupt system operations through denial of service or escalate their privileges within the operating environment. The vulnerability stems from improper handling of capabilities when setuid programs attempt to drop privileges, fundamentally undermining the security model that separates privileged and unprivileged execution contexts.
The technical flaw manifests in how the Linux kernel manages the relationship between capabilities and setuid operations, particularly when programs attempt to reduce their privilege level after gaining elevated rights. When a setuid program is executed with specific capabilities, the kernel's capability system fails to properly enforce privilege dropping mechanisms, allowing malicious users to maintain elevated privileges even after the program should have reverted to normal user permissions. This misconfiguration creates a persistent security boundary violation where the expected privilege separation between root and user contexts becomes compromised, enabling attackers to maintain access to privileged system resources beyond the normal program execution lifecycle.
The operational impact of this vulnerability extends beyond simple privilege escalation to include potential denial of service scenarios that can severely disrupt system availability. Local attackers can exploit this flaw to either prevent legitimate setuid programs from functioning correctly, thereby blocking essential system operations, or to maintain unauthorized elevated access indefinitely. The vulnerability affects the fundamental security architecture of Linux systems by undermining the core principle that setuid programs should drop privileges upon execution, creating persistent backdoors that could remain undetected for extended periods while providing attackers with continued access to privileged system functions.
This vulnerability aligns with CWE-250, which addresses "Execute Code with Unusual/Unanticipated Privileges" and relates to the broader category of privilege escalation flaws in operating system kernels. From an ATT&CK framework perspective, this vulnerability maps to T1068, "Local Port Forwarding," and T1548.001, "Abuse Elevation Control Mechanism," as it enables attackers to maintain elevated privileges through improper capability handling. The issue also connects to T1059, "Command and Scripting Interpreter," as attackers can leverage the persistent elevated access to execute commands with root privileges. Mitigation strategies should include immediate kernel upgrades to version 2.2.16 or later, proper capability management through the setcap utility, and implementation of strict privilege dropping policies for setuid programs. System administrators should also conduct comprehensive security audits to identify programs that may be vulnerable to this capability-based privilege escalation and ensure that all setuid programs properly implement privilege dropping mechanisms according to security best practices established by the Open Group and other industry standards.