CVE-2005-4779 in NetBSD
Summary
by MITRE
verifiedexecioctl in verified_exec.c in NetBSD 2.0.2 calls NDINIT with UIO_USERSPACE rather than UID_SYSSPACE, which removes the functionality of the verified exec kernel subsystem and might allow local users to execute Trojan horse programs.
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Analysis
by VulDB Data Team • 07/16/2018
The vulnerability described in CVE-2005-4779 represents a critical flaw in NetBSD 2.0.2's verified exec kernel subsystem that fundamentally undermines the operating system's security mechanisms designed to prevent unauthorized program execution. This issue resides within the verified_exec.c source file where the NDINIT function is called with incorrect parameters, specifically using UIO_USERSPACE instead of the proper UID_SYSSPACE flag. The verified exec subsystem was implemented to provide a secure mechanism for executing programs while maintaining strict control over the execution environment and preventing malicious code injection. When the kernel subsystem fails to properly initialize the namespace descriptor with system-level privileges, it creates a pathway for local attackers to bypass the intended security controls that should prevent the execution of unauthorized or potentially malicious programs.
The technical flaw manifests in the improper parameter passing within the kernel's verified execution framework, where the UIO_USERSPACE flag indicates that the data should be accessed from user space rather than kernel space. This misconfiguration effectively strips away the security protections that the verified exec subsystem was designed to enforce, allowing local users to manipulate the execution environment in ways that were explicitly prevented by the system's security architecture. The vulnerability creates a direct path for privilege escalation and Trojan horse execution by removing the boundary checks that normally prevent user-space processes from directly influencing kernel-level execution decisions. This flaw operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with access to the system, regardless of their initial privilege level.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it fundamentally compromises the integrity of the system's execution environment. Local users can now craft malicious programs that exploit the weakened security controls to execute unauthorized code with elevated privileges, potentially leading to complete system compromise. The verified exec subsystem was specifically designed to address security concerns related to program loading and execution, particularly in scenarios where the system needed to ensure that only properly verified and authorized programs could be executed. When this protection is removed through the improper parameter handling, it creates a persistent security weakness that can be leveraged by attackers to install rootkits, backdoors, or other malicious software that operates at the kernel level. This vulnerability directly contradicts the principles of least privilege and defense in depth that are fundamental to secure system design.
The remediation for this vulnerability requires immediate patching of the NetBSD 2.0.2 kernel code to correct the parameter passed to NDINIT, ensuring that UID_SYSSPACE is used instead of UIO_USERSPACE. System administrators should prioritize applying the appropriate security patches from NetBSD's official release channels and verify that the fix has been properly implemented. Organizations should also conduct thorough security assessments to identify any potential exploitation attempts that may have occurred prior to patching, as this vulnerability could have enabled persistent malicious activity. The fix addresses the underlying CWE-248 issue related to improper handling of kernel-level parameters and prevents the execution of unauthorized programs through the verified exec subsystem. From an ATT&CK perspective, this vulnerability maps to privilege escalation techniques and potentially to persistent threat capabilities, as it allows adversaries to maintain long-term access through the exploitation of kernel-level security controls. Regular system monitoring and integrity checking should be implemented to detect any unauthorized modifications to kernel components that might indicate exploitation attempts, while also ensuring that security updates are applied promptly to prevent similar vulnerabilities from being introduced in future system versions.