CVE-2014-8964 in Perl-compatible Regular Expression Library
Summary
by MITRE
Heap-based buffer overflow in PCRE 8.36 and earlier allows remote attackers to cause a denial of service (crash) or have other unspecified impact via a crafted regular expression, related to an assertion that allows zero repeats.
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Analysis
by VulDB Data Team • 04/07/2022
The vulnerability identified as CVE-2014-8964 represents a critical heap-based buffer overflow within the Perl Compatible Regular Expressions library version 8.36 and earlier. This flaw resides in the regular expression engine's handling of assertions that permit zero repeats, creating a condition where maliciously crafted regular expressions can trigger memory corruption during pattern compilation or execution. The vulnerability demonstrates characteristics consistent with CWE-121, heap-based buffer overflow, where insufficient bounds checking allows attackers to write beyond allocated memory boundaries.
The technical implementation of this vulnerability occurs when PCRE processes regular expressions containing assertions that allow zero repetitions, such as the * quantifier applied to assertion constructs. During the parsing and compilation phase, the library fails to properly validate the memory allocation required for handling these specific patterns, leading to a situation where attacker-controlled input can cause the heap allocator to write data beyond the intended buffer boundaries. This memory corruption manifests as either a crash due to heap corruption or potentially more severe consequences depending on the execution environment and memory layout.
From an operational perspective, this vulnerability presents significant risk to systems relying on PCRE for pattern matching operations, particularly those processing untrusted input from web applications, network devices, or any system accepting user-supplied regular expressions. The remote exploitation capability means that attackers can trigger the vulnerability from external networks without requiring local access, making it particularly dangerous for web-facing services. The impact extends beyond simple denial of service to potentially allow for more sophisticated attacks depending on the target environment and memory protection mechanisms in place.
The vulnerability aligns with ATT&CK technique T1059.007 for Application Layer Protocol and T1211 for Exploitation for Defense Evasion, as it enables attackers to manipulate application behavior through crafted input. Organizations using affected versions of PCRE should prioritize immediate patching to address this vulnerability, as the attack surface includes any system processing regular expressions from untrusted sources. The remediation strategy should include updating to PCRE version 8.37 or later, implementing input validation and sanitization measures, and monitoring for potential exploitation attempts. Additionally, systems should consider implementing application-level protections such as resource limits and memory protection mechanisms to mitigate potential impact if exploitation occurs.