CVE-2014-9769 in PCRE
Summary
by MITRE
pcre_jit_compile.c in PCRE 8.35 does not properly use table jumps to optimize nested alternatives, which allows remote attackers to cause a denial of service (stack memory corruption) or possibly have unspecified other impact via a crafted string, as demonstrated by packets encountered by Suricata during use of a regular expression in an Emerging Threats Open ruleset.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability described in CVE-2014-9769 resides within the PCRE (Perl Compatible Regular Expressions) library version 8.35, specifically in the pcre_jit_compile.c module responsible for just-in-time compilation optimizations. This flaw represents a critical security issue that affects the library's handling of nested alternatives during JIT compilation processes, creating potential pathways for remote exploitation through carefully crafted input strings. The vulnerability manifests when the library fails to properly implement table jumps, which are optimization techniques designed to improve performance by reducing the number of conditional checks during pattern matching operations. When these optimizations are improperly applied to nested alternatives, the resulting code generation can lead to stack memory corruption during regular expression processing.
The technical implementation of this vulnerability stems from how PCRE's JIT compiler handles nested alternatives within regular expressions, particularly when these patterns are processed through the table jump optimization mechanism. Table jumps are typically used to create efficient jump tables that allow the processor to quickly navigate to the appropriate code path based on input characteristics. However, in this specific case, the implementation fails to properly account for the nested structure of alternatives, leading to incorrect jump table generation. This misconfiguration causes the JIT compiler to generate code that may attempt to access memory locations beyond the allocated stack space, resulting in stack corruption that can manifest as application crashes or potentially more severe memory corruption issues. The vulnerability is particularly dangerous because it can be triggered through network traffic processing, making it exploitable in network-based applications like intrusion detection systems and web servers.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as demonstrated by its exploitation in Suricata network intrusion detection system. When attackers craft specific strings that trigger the flawed JIT compilation path, they can cause the target application to crash or corrupt memory in ways that may allow for more sophisticated attacks. The vulnerability affects any application that utilizes PCRE 8.35 or earlier versions for regular expression processing, particularly those handling untrusted input such as web applications, network security tools, and log analysis systems. The potential for unspecified other impacts suggests that under certain conditions, this memory corruption could potentially be leveraged for code execution or privilege escalation, making it a serious concern for security-conscious organizations. The vulnerability's exploitation through network traffic processing makes it particularly relevant for organizations running network security appliances, web servers, or any system that processes regular expressions from external sources.
Mitigation strategies for CVE-2014-9769 primarily focus on upgrading to PCRE version 8.36 or later, where the JIT compilation issues have been addressed through proper implementation of table jump optimizations. Organizations should also implement input validation and sanitization measures to reduce the risk of exploitation, particularly when processing untrusted regular expressions. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and may map to ATT&CK techniques involving privilege escalation and denial of service through memory corruption. Additionally, organizations should consider implementing network segmentation and monitoring to detect potential exploitation attempts, as well as ensuring that all systems processing regular expressions are regularly updated with the latest security patches. The fix implemented in PCRE 8.36 specifically addresses the table jump optimization logic to prevent improper memory access patterns while maintaining the performance benefits of JIT compilation.