CVE-2007-4768 in Flash Player
Summary
by MITRE
Heap-based buffer overflow in Perl-Compatible Regular Expression (PCRE) library before 7.3 allows context-dependent attackers to execute arbitrary code via a singleton Unicode sequence in a character class in a regex pattern, which is incorrectly optimized.
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Analysis
by VulDB Data Team • 07/30/2019
The vulnerability identified as CVE-2007-4768 represents a critical heap-based buffer overflow within the Perl-Compatible Regular Expression library version 7.2 and earlier. This flaw exists in the optimization phase of regex pattern processing where singleton Unicode sequences within character classes are handled incorrectly. The vulnerability is context-dependent, meaning its exploitation requires specific conditions related to the input pattern structure and the Unicode handling capabilities of the affected system.
The technical implementation of this vulnerability stems from improper memory management during the compilation and optimization of regular expressions containing Unicode character classes. When PCRE processes a regex pattern that includes a singleton Unicode sequence within a character class, the library's optimization algorithm fails to properly account for the memory requirements needed to store the expanded Unicode character representation. This miscalculation results in a buffer overflow condition where data written to heap memory exceeds the allocated buffer boundaries, potentially allowing attackers to overwrite adjacent memory locations.
The operational impact of this vulnerability extends beyond simple code execution, as it can be leveraged to achieve arbitrary code execution on systems utilizing vulnerable versions of the PCRE library. Attackers can craft malicious regex patterns that, when processed by the vulnerable library, trigger the buffer overflow condition. This allows for potential privilege escalation, system compromise, or denial of service conditions depending on the execution environment and the specific implementation of the vulnerable software. The vulnerability affects a wide range of applications that rely on PCRE for pattern matching, including web servers, network security appliances, and various system utilities.
Security professionals should prioritize updating all systems using PCRE libraries to version 7.3 or later, which contains the necessary patches to address this heap-based buffer overflow. Additionally, input validation and sanitization measures should be implemented at the application level to prevent malicious regex patterns from reaching the vulnerable library. The vulnerability aligns with CWE-121, heap-based buffer overflow, and can be categorized under ATT&CK technique T1059.007 for execution through scripting languages, making it a significant concern for organizations relying on regular expression processing for security filtering and data validation.
The exploitation of this vulnerability demonstrates the importance of proper memory management in cryptographic and text processing libraries. The issue highlights how optimization routines can introduce security flaws when they fail to account for the expanded memory requirements of Unicode character handling. Organizations should conduct comprehensive vulnerability assessments to identify all systems using vulnerable PCRE versions and implement robust patch management procedures to ensure timely remediation of such critical security flaws.