CVE-2013-4220 in Linux
Summary
by MITRE
The bad_mode function in arch/arm64/kernel/traps.c in the Linux kernel before 3.9.5 on the ARM64 platform allows local users to cause a denial of service (system crash) via vectors involving an attempted register access that triggers an unexpected value in the Exception Syndrome Register (ESR).
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Analysis
by VulDB Data Team • 05/08/2018
The vulnerability described in CVE-2013-4220 represents a critical flaw in the Linux kernel's ARM64 architecture implementation that specifically affects systems running kernel versions prior to 3.9.5. This issue resides within the bad_mode function located in arch/arm64/kernel/traps.c, which serves as a crucial error handling mechanism for the ARM64 platform. The vulnerability stems from inadequate validation of exception syndrome register values during exception handling, creating a path where malicious or malformed system calls can trigger unexpected behavior in the kernel's trap handling subsystem.
The technical flaw manifests when the bad_mode function encounters an exception scenario involving register access operations that result in an unexpected value within the Exception Syndrome Register. This register contains essential information about the exception that occurred, including the type of exception, the instruction that caused it, and other relevant contextual data. When the kernel's trap handler fails to properly validate or handle these unexpected ESR values, it can lead to a kernel panic or system crash, effectively causing a denial of service condition that renders the entire system inoperable. The vulnerability specifically exploits the lack of proper bounds checking and value validation in the kernel's exception handling code path.
The operational impact of this vulnerability extends beyond simple system crashes, as it provides local attackers with a reliable method to induce denial of service conditions on ARM64-based systems. This affects any device or platform running Linux kernel versions before 3.9.5, including servers, embedded systems, and mobile devices that utilize ARM64 architecture. The vulnerability is particularly concerning because it requires minimal privileges to exploit, as local users can trigger the condition through normal system operation without requiring elevated permissions. This makes it a significant threat in environments where local access is possible, potentially allowing attackers to disrupt services or cause system downtime in critical infrastructure deployments.
From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of input ranges, and demonstrates characteristics consistent with ATT&CK technique T1499.004 related to network denial of service. The vulnerability's exploitation pathway follows a classic kernel exploitation pattern where improper error handling leads to system instability. Organizations should prioritize patching affected systems with kernel versions 3.9.5 or later, which include the necessary fixes to properly validate ESR values and prevent the unexpected behavior that leads to system crashes. Additionally, system administrators should implement monitoring for unusual system crash patterns and consider implementing kernel hardening measures to reduce the attack surface for similar vulnerabilities in the future.