CVE-2006-7230 in PCRE
Summary
by MITRE
Perl-Compatible Regular Expression (PCRE) library before 7.0 does not properly calculate the amount of memory needed for a compiled regular expression pattern when the (1) -x or (2) -i UTF-8 options change within the pattern, which allows context-dependent attackers to cause a denial of service (PCRE or glibc crash) via crafted regular expressions.
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Analysis
by VulDB Data Team • 08/01/2019
The vulnerability identified as CVE-2006-7230 affects the Perl-Compatible Regular Expression library version 7.0 and earlier, representing a critical memory management flaw that can lead to denial of service conditions. This issue specifically manifests when regular expression patterns contain UTF-8 options such as -x or -i that change within the pattern structure, creating a scenario where the library miscalculates required memory allocation for compiled patterns. The flaw falls under the category of improper memory allocation as classified by CWE-704, which directly impacts the library's ability to handle memory resources correctly during pattern compilation processes.
The technical implementation of this vulnerability stems from the PCRE library's internal memory calculation algorithms that fail to account for the dynamic nature of UTF-8 option changes within regular expressions. When these options -x (extended) or -i (case insensitive) are encountered within a pattern, the library's memory estimation routine becomes confused about the actual memory requirements needed for the compiled bytecode representation. This miscalculation can result in either insufficient memory allocation leading to buffer overflows or excessive memory consumption that triggers system instability. The vulnerability is context-dependent, meaning it requires specific patterns that contain the problematic UTF-8 option changes to manifest, making it particularly challenging to detect during routine security assessments.
The operational impact of this vulnerability extends beyond simple denial of service conditions, potentially affecting systems that rely heavily on regular expression processing for text parsing, validation, and pattern matching operations. When exploited, the vulnerability can cause crashes in both the PCRE library itself and dependent systems such as glibc, creating cascading failures that may affect web servers, email systems, and other applications that utilize regular expression processing. The attack vector involves crafting specially designed regular expressions that trigger the memory calculation error, making this vulnerability particularly dangerous in environments where users can submit arbitrary input patterns, such as web applications or content management systems. According to ATT&CK framework category T1499, this represents a resource exhaustion technique that can be leveraged to disrupt system availability.
Mitigation strategies for this vulnerability require immediate patching of affected systems to upgrade to PCRE version 7.0 or later where the memory calculation issue has been resolved. System administrators should also implement input validation measures to restrict the complexity and length of regular expressions processed by applications, particularly in environments where user input is accepted. Additionally, monitoring for unusual memory consumption patterns and implementing proper error handling mechanisms can help detect exploitation attempts. Organizations should conduct comprehensive vulnerability assessments to identify all systems using affected PCRE versions and ensure that regular expression processing components are properly configured to prevent malicious input from triggering memory allocation errors. The fix implemented in PCRE 7.0 addresses the root cause by improving memory estimation algorithms to properly account for UTF-8 option changes within patterns, thereby preventing the miscalculations that led to system crashes and denial of service conditions.