CVE-2005-3257 in Linux
Summary
by MITRE
The VT implementation (vt_ioctl.c) in Linux kernel 2.6.12, and possibly other versions including 2.6.14.4, allows local users to use the KDSKBSENT ioctl on terminals of other users and gain privileges, as demonstrated by modifying key bindings using loadkeys.
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Analysis
by VulDB Data Team • 12/30/2024
The vulnerability described in CVE-2005-3257 represents a critical privilege escalation flaw within the Linux kernel's virtual terminal implementation. This issue specifically affects the vt_ioctl.c component that manages virtual terminal operations, where local attackers can exploit a design flaw to manipulate terminal key bindings of other users. The vulnerability stems from insufficient access controls and validation mechanisms within the kernel's terminal handling subsystem, creating an avenue for unauthorized privilege elevation through seemingly benign terminal operations.
The technical exploitation occurs through the KDSKBSENT ioctl command which is designed to set keyboard sent events for virtual terminals. When a local user executes this ioctl on another user's terminal, the kernel fails to properly verify ownership or permissions, allowing arbitrary modification of key bindings. This capability becomes particularly dangerous when combined with the loadkeys utility, which can interpret and apply these modified key bindings to execute malicious commands or establish persistent access mechanisms. The vulnerability operates at the kernel level, bypassing standard user-space permission checks and directly manipulating terminal state information.
From an operational perspective, this vulnerability enables local users to escalate privileges by modifying keyboard mappings that could be leveraged for malicious purposes. Attackers can craft key bindings that execute arbitrary commands when specific key combinations are pressed, potentially allowing them to gain root access or establish backdoors. The impact extends beyond simple privilege escalation as it can be used to maintain persistent access to systems, create covert communication channels, or disable security mechanisms through terminal manipulation. This vulnerability particularly affects multi-user systems where users share the same physical or virtual terminal infrastructure.
The security implications of CVE-2005-3257 align with CWE-284, which addresses improper access control mechanisms, and can be mapped to ATT&CK techniques involving privilege escalation and persistence. The vulnerability demonstrates a classic case of insufficient privilege checking in kernel space operations, where the lack of proper user isolation and terminal ownership verification creates an exploitable condition. Mitigation strategies should include kernel updates to versions that properly enforce terminal access controls, implementation of additional monitoring for unauthorized terminal modifications, and system hardening measures that restrict access to terminal control interfaces. Organizations should also consider implementing proper user session management and terminal isolation mechanisms to prevent cross-user terminal manipulation. The vulnerability highlights the importance of robust kernel-level access control implementations and serves as a reminder of the critical security implications when privilege escalation paths exist within core system components.