CVE-2017-7246 in PCRE
Summary
by MITRE
Stack-based buffer overflow in the pcre32_copy_substring function in pcre_get.c in libpcre1 in PCRE 8.40 allows remote attackers to cause a denial of service (WRITE of size 268) or possibly have unspecified other impact via a crafted file.
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Analysis
by VulDB Data Team • 11/15/2022
The vulnerability CVE-2017-7246 represents a critical stack-based buffer overflow affecting the perl compatible regular expressions library version 8.40. This flaw exists within the pcre32_copy_substring function located in the pcre_get.c source file, which forms part of the libpcre1 library implementation. The vulnerability manifests when processing crafted input files that trigger the buffer overflow condition during regular expression pattern matching operations. The specific memory corruption occurs through a write operation of size 268 bytes, indicating the overflow extends beyond the allocated stack buffer boundaries. This type of vulnerability falls under the CWE-121 stack-based buffer overflow category, which is classified as a fundamental memory safety issue that can lead to arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable more severe security consequences. Remote attackers can exploit this flaw by crafting malicious input files that, when processed by applications utilizing the affected libpcre1 library, trigger the buffer overflow condition. The vulnerability's reach is significant as it affects any software system that relies on PCRE 8.40 for regular expression processing, including web servers, email filters, intrusion detection systems, and various network security appliances. The write operation of 268 bytes suggests that the overflow could potentially overwrite adjacent stack variables or return addresses, creating opportunities for privilege escalation or arbitrary code execution depending on the specific system configuration and memory layout.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage, as it enables attackers to manipulate regular expression processing components that may be used in automated security systems or application logic. The vulnerability's exploitation pathway typically involves input validation bypass through malformed regular expression patterns that cause the pcre32_copy_substring function to write beyond its intended buffer boundaries. Security professionals should note that this vulnerability affects the core parsing functionality of PCRE, making it particularly dangerous as it can be triggered through various application interfaces that utilize regular expressions for input validation, data parsing, or pattern matching operations.
Mitigation strategies for CVE-2017-7246 primarily focus on immediate remediation through library updates and application-level protections. Organizations must upgrade to PCRE version 8.41 or later, which contains the necessary patches to address the buffer overflow condition. Additionally, implementing input validation controls and restricting regular expression processing in security-critical applications can help reduce the attack surface. Network segmentation and application sandboxing techniques can provide additional layers of protection by limiting the potential impact of successful exploitation attempts. Security monitoring should include detection of unusual memory access patterns and potential buffer overflow indicators in system logs, particularly in applications that process untrusted input through regular expression engines. The vulnerability underscores the importance of maintaining up-to-date third-party libraries and implementing comprehensive security testing procedures that include static and dynamic analysis of input processing components.