CVE-2011-2693 in Red Hat
Summary
by MITRE
The perf subsystem in the kernel package 2.6.32-122.el6.x86_64 in Red Hat Enterprise Linux (RHEL) 6 does not properly handle NMIs, which might allow local users to cause a denial of service (excessive log messages) via unspecified vectors.
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Analysis
by VulDB Data Team • 01/03/2022
The vulnerability identified as CVE-2011-2693 resides within the performance monitoring unit subsystem of the Linux kernel, specifically affecting Red Hat Enterprise Linux version 6 with kernel package 2.6.32-122.el6.x86_64. This issue represents a critical flaw in how the kernel handles non-maskable interrupts which are essential for system monitoring and debugging operations. The perf subsystem serves as a comprehensive performance analysis framework that provides detailed insights into system behavior through hardware performance counters and software event monitoring. When the kernel receives NMIs, these interrupts are designed to be processed with high priority and immediate attention, typically for critical system events such as hardware errors or debugging purposes. The improper handling of these interrupts within the perf subsystem creates a scenario where malicious or unintended processing can occur, leading to excessive logging behavior that can overwhelm system resources and potentially cause system instability.
The technical flaw manifests in the kernel's inability to properly manage the state and processing of NMIs when they interact with the perf subsystem. This vulnerability stems from inadequate input validation and state management within the interrupt handling code paths. When NMIs are received while the perf subsystem is active, the kernel's response mechanism fails to properly sanitize or limit the processing of these interrupts, resulting in a cascading effect where numerous log messages are generated in rapid succession. The flaw operates at the kernel level, making it particularly dangerous as it can be exploited by local users who have access to the system, requiring no special privileges beyond basic user accounts. This represents a classic denial of service vulnerability where the attacker can consume system resources through excessive logging, effectively rendering the system unresponsive to legitimate operations while filling up disk space and overwhelming system logs.
The operational impact of CVE-2011-2693 extends beyond simple service disruption, creating potential cascading failures within system monitoring and logging infrastructure. When the perf subsystem generates excessive log messages due to improper NMI handling, it can cause system administrators to lose visibility into genuine system issues as log files become flooded with repetitive entries. The vulnerability affects the fundamental interrupt handling mechanism that underpins system stability, potentially leading to system crashes or severe performance degradation. This issue is particularly concerning in enterprise environments where system reliability is paramount, as it can affect mission-critical applications that depend on consistent system behavior. The vulnerability also creates opportunities for attackers to exhaust system resources through sustained log flooding, making it a potential vector for resource exhaustion attacks that can impact availability.
Mitigation strategies for CVE-2011-2693 focus primarily on applying the appropriate kernel security patches released by Red Hat. System administrators should immediately update their RHEL 6 systems to the latest kernel versions that contain fixes for this vulnerability, typically through standard update mechanisms or by applying the specific errata patches provided by Red Hat. Additionally, implementing monitoring and alerting systems can help detect unusual logging patterns that might indicate exploitation attempts. Organizations should also consider implementing resource limits on log file sizes and rotation policies to prevent complete system exhaustion. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and relates to ATT&CK technique T1499.001 for resource exhaustion attacks. System hardening measures including disabling unnecessary perf subsystem features and restricting access to performance monitoring capabilities can further reduce the attack surface. Regular security audits and vulnerability assessments should include verification that systems are running patched kernel versions to prevent exploitation of this and similar interrupt handling vulnerabilities that could compromise system availability and stability.