CVE-2016-4973 in GCC for Stack Smashing Protection
Summary
by MITRE
Binaries compiled against targets that use the libssp library in GCC for stack smashing protection (SSP) might allow local users to perform buffer overflow attacks by leveraging lack of the Object Size Checking feature.
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Analysis
by VulDB Data Team • 10/14/2019
The vulnerability identified as CVE-2016-4973 stems from a critical weakness in the stack smashing protection mechanisms implemented through the libssp library in the GNU Compiler Collection. This issue specifically affects binaries that are compiled with GCC's stack smashing protection features but lack proper object size checking capabilities. The fundamental flaw lies in the incomplete implementation of stack canary mechanisms that should prevent buffer overflow exploits by detecting potential stack corruption attempts.
The technical nature of this vulnerability creates a dangerous gap in memory protection where the stack canary values are not properly validated against the actual object sizes during runtime. This omission allows local attackers to craft buffer overflow payloads that can bypass the intended security measures. When a program is compiled with libssp but without the necessary object size checking, the compiler cannot effectively verify that buffer operations remain within allocated boundaries, creating exploitable conditions for malicious code execution.
From an operational perspective, this vulnerability significantly increases the attack surface for local privilege escalation and arbitrary code execution within affected systems. The lack of object size checking means that even programs that appear to be properly protected through stack smashing prevention can still be compromised through carefully constructed buffer overflow attacks. This weakness particularly impacts systems where privilege escalation is possible, as attackers can leverage this vulnerability to gain elevated system privileges and potentially compromise entire system environments.
The vulnerability maps directly to CWE-121, which describes stack-based buffer overflow conditions, and aligns with ATT&CK technique T1068, which covers "Exploitation for Privilege Escalation." Organizations affected by this vulnerability should immediately implement comprehensive patch management procedures to update all systems running GCC compiled binaries. The recommended mitigation involves ensuring that all affected systems are updated with patched versions of GCC and libssp that properly implement object size checking. Additionally, system administrators should review and audit existing binaries to identify those compiled with vulnerable configurations and recompile them with proper security flags to enable complete stack smashing protection mechanisms.
The broader implications of this vulnerability extend beyond individual system compromises, as it represents a fundamental flaw in compiler-level security implementations that can affect numerous applications and systems. This weakness demonstrates the critical importance of comprehensive security testing during the compilation process and highlights the necessity of maintaining up-to-date development toolchains to prevent exploitation of such foundational security mechanisms.