CVE-2006-1902 in gcc
Summary
by MITRE
fold_binary in fold-const.c in GNU Compiler Collection (gcc) 4.1 improperly handles pointer overflow when folding a certain expr comparison to a corresponding offset comparison in cases other than EQ_EXPR and NE_EXPR, which might introduce buffer overflow vulnerabilities into applications that could be exploited by context-dependent attackers.NOTE: the vendor states that the essence of the issue is "not correctly interpreting an offset to a pointer as a signed value."
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Analysis
by VulDB Data Team • 07/24/2018
The vulnerability identified as CVE-2006-1902 resides within the GNU Compiler Collection version 4.1, specifically in the fold_binary function located in fold-const.c. This flaw represents a critical issue in the compiler's constant folding optimization process where pointer overflow conditions are not properly handled during expression comparison operations. The vulnerability manifests when the compiler attempts to fold certain expression comparisons into corresponding offset comparisons, but fails to correctly interpret pointer offsets as signed values in scenarios beyond equality and inequality comparisons. This fundamental misinterpretation of signed versus unsigned pointer arithmetic creates a pathway for buffer overflow conditions that can be exploited by context-dependent attackers.
The technical nature of this vulnerability stems from the compiler's improper handling of pointer arithmetic during optimization phases. When gcc encounters specific binary expressions involving pointers, it attempts to optimize these expressions by converting them into offset comparisons. However, the fold_binary function fails to properly account for the signed nature of pointer offsets in comparison operations other than EQ_EXPR and NE_EXPR. This oversight leads to incorrect assumptions about the arithmetic properties of pointer values, particularly when dealing with pointer subtraction operations that should maintain signed integer characteristics. The vulnerability is categorized under CWE-191 Integer Underflow/Overflow, specifically relating to improper handling of signed integer operations. According to ATT&CK framework, this maps to technique T1059.008 for compiler-based attacks and T1203 for exploitation of software vulnerabilities through code generation flaws.
The operational impact of this vulnerability extends beyond simple compilation issues, as it fundamentally compromises the security of applications built with affected compiler versions. When applications are compiled with gcc 4.1, the improperly optimized code may contain buffer overflow vulnerabilities that manifest at runtime, particularly in scenarios involving pointer arithmetic and memory access patterns. Attackers can exploit this weakness by crafting specific code patterns that trigger the compiler's flawed optimization, potentially leading to arbitrary code execution or denial of service conditions. The vulnerability is particularly dangerous because it operates at the compilation level, meaning that even legitimate applications compiled with the affected compiler could contain exploitable buffer overflow conditions that are not apparent during source code analysis.
Mitigation strategies for CVE-2006-1902 require immediate compiler upgrades to versions that address the pointer overflow handling in fold_binary function. System administrators and developers should prioritize updating to gcc versions that have patched this specific issue, typically gcc 4.1.2 or later releases which contain the necessary corrections to properly handle signed pointer arithmetic during constant folding operations. Additionally, organizations should implement comprehensive code review processes to identify and remediate any existing applications compiled with the vulnerable compiler version. The fix implemented by the gcc development team specifically addresses the incorrect interpretation of pointer offsets as signed values, ensuring that all comparison operations maintain proper arithmetic semantics throughout the optimization process. Security teams should also consider implementing runtime protections such as stack canaries and address space layout randomization to provide additional defense in depth against potential exploitation of any remaining vulnerabilities in legacy codebases.