CVE-2005-0135 in Linux
Summary
by MITRE
The unw_unwind_to_user function in unwind.c on Itanium (ia64) architectures in Linux kernel 2.6 allows local users to cause a denial of service (system crash).
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Analysis
by VulDB Data Team • 05/31/2019
The vulnerability identified as CVE-2005-0135 resides within the Linux kernel's unwinding mechanism on Itanium (ia64) architectures, specifically within the unw_unwind_to_user function located in the unwind.c source file. This flaw represents a critical denial of service vulnerability that can be exploited by local attackers to crash the entire system. The issue stems from improper handling of unwind operations when transitioning from kernel space back to user space, creating a condition where malformed or unexpected unwind contexts can trigger system instability.
The technical implementation of this vulnerability involves the kernel's exception handling and stack unwinding subsystem that manages the process of traversing call frames during exception processing or system debugging. On ia64 architectures, the unwind mechanism maintains detailed metadata about function call stacks in the form of unwind tables that describe how to recover stack pointers and register states. The unw_unwind_to_user function specifically handles the transition of control flow from kernel mode back to user mode, and it contains a flaw in its validation logic that fails to properly sanitize input parameters or unwind table entries. When an attacker can manipulate the unwind context inappropriately, the function may attempt to access invalid memory locations or execute malformed unwind operations that cause the kernel to panic and crash.
This vulnerability operates at the kernel level and affects systems running Linux kernel versions 2.6 and earlier on Itanium hardware platforms. The impact extends beyond simple system instability as it can be exploited to create persistent denial of service conditions that may require manual system rebooting to restore normal operation. The local privilege requirement means that any user with access to the system can potentially exploit this vulnerability, making it particularly dangerous in multi-user environments or systems where untrusted users have shell access. The vulnerability directly maps to CWE-129, which describes improper validation of input boundaries, and aligns with ATT&CK technique T1499.004 for network denial of service, though in this case it manifests as a system-level crash rather than network disruption.
The operational impact of this vulnerability extends to system reliability and availability, particularly in mission-critical environments where system uptime is essential. Organizations running Itanium-based Linux systems may experience unexpected system crashes that can result in data loss, service interruptions, and increased administrative overhead for system recovery. The vulnerability can be particularly problematic in server environments where multiple users or processes may be running simultaneously, as a single exploited instance can bring down the entire system. Mitigation strategies include applying kernel patches that properly validate unwind table entries and input parameters, implementing kernel lockdown mechanisms, and employing system monitoring to detect potential exploitation attempts. System administrators should prioritize updating to patched kernel versions and consider implementing additional security controls such as restricted user privileges and enhanced logging to detect anomalous unwind operations that might indicate attempted exploitation.