CVE-2014-7186 in Mac OS X
Summary
by MITRE
The redirection implementation in parse.y in GNU Bash through 4.3 bash43-026 allows remote attackers to cause a denial of service (out-of-bounds array access and application crash) or possibly have unspecified other impact via crafted use of here documents, aka the "redir_stack" issue.
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Analysis
by VulDB Data Team • 12/01/2024
The vulnerability identified as CVE-2014-7186 represents a critical flaw in the GNU Bash shell implementation that affects versions through 4.3 bash43-026. This issue resides within the parse.y file's redirection handling mechanism, specifically concerning how the shell processes here documents. The flaw manifests as an out-of-bounds array access condition that can be exploited by remote attackers to trigger denial of service conditions or potentially achieve more severe impacts through crafted input sequences. The vulnerability is particularly dangerous because it operates at the parsing level of the shell, making it accessible through various attack vectors that involve shell command execution.
The technical root cause of this vulnerability stems from improper bounds checking within the redir_stack implementation, which is responsible for managing redirection operations in bash. When processing here documents, the shell maintains an array-based stack structure to track redirection operations, but fails to validate array indices properly during certain parsing scenarios. This allows attackers to craft specific input sequences that cause the parser to access memory locations beyond the allocated array boundaries. The flaw operates through the shell's command parsing logic where here documents are processed in a manner that can be manipulated to trigger the out-of-bounds access condition.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attack scenarios. Remote attackers can leverage this weakness to crash the bash process, causing service disruption to systems that rely on shell execution for various operations. In some cases, the vulnerability may allow for arbitrary code execution or privilege escalation depending on how the shell is utilized within the target environment. Systems running vulnerable bash versions are particularly at risk when they process untrusted input through shell commands, including web applications, automated scripts, or any service that invokes bash for command processing.
Mitigation strategies for CVE-2014-7186 primarily focus on updating to patched versions of GNU Bash where the array bounds checking has been properly implemented. The official fix addresses the specific redir_stack implementation by adding proper validation checks before array access operations. Organizations should prioritize patching affected systems, particularly those exposed to untrusted input or remote attack surfaces. Additional defensive measures include implementing input validation for shell command execution, using restricted shell environments, and employing proper sandboxing techniques to limit the potential impact of exploitation attempts. This vulnerability aligns with CWE-129, which addresses improper validation of array indices, and maps to ATT&CK technique T1059.004 for bash command execution, highlighting the importance of proper shell input handling in security defenses.
The broader implications of this vulnerability underscore the critical importance of proper memory management in shell implementations and demonstrate how parsing flaws can lead to severe security consequences. The issue affects systems where bash is used for command execution, making it particularly relevant for web servers, automated systems, and any environment where shell-based command processing occurs. Security teams should conduct comprehensive vulnerability assessments to identify systems running vulnerable bash versions and ensure proper patch management procedures are in place to prevent exploitation of similar parsing vulnerabilities in other software components.