CVE-2011-1769 in SystemTap
Summary
by MITRE
SystemTap 1.4 and earlier, when unprivileged (aka stapusr) mode is enabled, allows local users to cause a denial of service (divide-by-zero error and OOPS) via a crafted ELF program with DWARF expressions that are not properly handled by a stap script that performs context variable access.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability identified as CVE-2011-1769 resides within SystemTap version 1.4 and earlier implementations, specifically when operating in unprivileged mode known as stapusr mode. This security flaw represents a significant concern for system administrators and security professionals as it demonstrates how seemingly benign debugging and profiling tools can be exploited to create system instability. The vulnerability arises from insufficient validation of debugging information within ELF programs, particularly when these programs contain DWARF expressions that are not adequately handled by SystemTap scripts during context variable access operations.
The technical mechanism behind this vulnerability involves a divide-by-zero error and subsequent kernel OOPS condition that occurs when SystemTap processes ELF files containing malformed DWARF expressions. When unprivileged mode is enabled, the stapusr user context has limited but still significant access to system profiling capabilities. The flaw manifests when a crafted ELF program with specific DWARF expressions is processed by a stap script that attempts to access context variables. This scenario creates a condition where the arithmetic operations within the debugging information trigger a division by zero exception, leading to a kernel panic or system crash. The underlying issue stems from inadequate input sanitization and error handling within the SystemTap kernel modules that process debugging data.
From an operational perspective, this vulnerability presents a serious denial of service threat that can be exploited by local users with minimal privileges. The impact extends beyond simple service interruption as the divide-by-zero error and OOPS conditions can potentially lead to complete system instability, requiring manual intervention to restore normal operations. This vulnerability directly affects the reliability and availability of systems that rely on SystemTap for performance monitoring and debugging purposes, particularly in production environments where system uptime is critical. The attack vector requires only local access and the ability to execute a crafted ELF program, making it accessible to users who might not possess elevated privileges but still have access to the system.
The vulnerability maps to CWE-369, which specifically addresses the issue of divide by zero errors in software systems, and relates to CWE-20, which covers input validation weaknesses in software applications. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and denial of service, though the initial access requires only local user privileges. The exploitation pattern demonstrates how debugging tools can be weaponized to create system instability, which aligns with ATT&CK technique T1499.004 related to network denial of service. Organizations should consider implementing mitigations that include disabling unprivileged mode when not required, updating to patched versions of SystemTap, and monitoring for unusual system behavior that might indicate exploitation attempts. The vulnerability also highlights the importance of proper input validation in kernel modules and the need for comprehensive testing of debugging and profiling tools in production environments.