CVE-2017-8786 in PCRE2
Summary
by MITRE
pcre2test.c in PCRE2 10.23 allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via a crafted regular expression.
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Analysis
by VulDB Data Team • 09/24/2020
The vulnerability identified as CVE-2017-8786 represents a critical heap-based buffer overflow flaw within the PCRE2 regular expression library version 10.23. This issue manifests in the pcre2test.c utility, which serves as a test program for the PCRE2 library but can be exploited to compromise systems running vulnerable versions. The flaw stems from inadequate input validation and memory management when processing specially crafted regular expressions, creating a potential attack vector for remote adversaries seeking to disrupt system operations or execute arbitrary code.
The technical implementation of this vulnerability involves the manipulation of regular expression parsing logic within the PCRE2 library. When the pcre2test.c utility encounters malformed or specially constructed regular expressions, the underlying parsing algorithms fail to properly bounds-check memory allocations, leading to heap corruption through buffer overflow conditions. This type of vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, though the heap-based nature of this particular flaw requires different mitigation approaches. The vulnerability can be triggered through any mechanism that allows input processing of regular expressions, including web applications, command-line interfaces, or automated tools that utilize the PCRE2 library.
The operational impact of CVE-2017-8786 extends beyond simple denial of service scenarios, as the heap corruption can potentially lead to arbitrary code execution or system instability. Remote attackers can exploit this vulnerability by submitting malicious regular expressions to applications that utilize the vulnerable PCRE2 library, making it particularly dangerous in web applications, network services, or any environment where user input is processed through regular expression engines. The vulnerability affects systems running PCRE2 version 10.23 and earlier, with the potential for exploitation across various platforms where the library is deployed. This flaw aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as it can enable adversaries to execute malicious code through vulnerable regular expression processing.
Organizations should prioritize immediate patching of affected systems, as PCRE2 version 10.24 and later contain fixes for this vulnerability. The mitigation strategy involves not only updating the library to a secure version but also implementing proper input validation and sanitization for all regular expression processing within applications. Security measures should include monitoring for suspicious regular expression patterns and implementing rate limiting or input size restrictions to prevent exploitation attempts. Additionally, system administrators should consider implementing network segmentation and access controls to limit exposure of vulnerable applications. The vulnerability demonstrates the importance of proper memory management in cryptographic and text processing libraries, as highlighted in industry best practices for secure coding and vulnerability management.