CVE-2017-7245 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 4) or possibly have unspecified other impact via a crafted file.
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Analysis
by VulDB Data Team • 11/15/2022
The vulnerability identified as CVE-2017-7245 represents a critical stack-based buffer overflow within the PCRE library's pcre32_copy_substring function located in pcre_get.c. This flaw exists in libpcre1 version 8.40 and affects the regular expression processing capabilities of applications that utilize PCRE for pattern matching operations. The vulnerability manifests when the library processes malformed input data through the pcre32_copy_substring function, which is responsible for copying substring data during regular expression matching processes. The buffer overflow occurs due to inadequate bounds checking during memory allocation and data copying operations, allowing attackers to write beyond the allocated stack buffer boundaries.
The technical exploitation of this vulnerability requires careful crafting of input data that triggers the specific code path within the pcre32_copy_substring function. When malicious input is processed, the function fails to properly validate the size of data being copied to the stack buffer, resulting in a write operation of size 4 bytes that overflows the allocated memory space. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue where data written to a buffer exceeds its allocated bounds. The vulnerability can be leveraged by remote attackers to cause denial of service conditions by corrupting memory structures, potentially leading to application crashes or system instability. In some scenarios, the overflow may allow for more sophisticated attacks including arbitrary code execution, though the primary impact documented is denial of service.
The operational impact of CVE-2017-7245 extends across numerous applications and systems that depend on PCRE for regular expression processing. Since PCRE is widely used in web servers, email filters, intrusion detection systems, and various security applications, the vulnerability presents a significant risk to system availability and stability. Attackers can exploit this flaw by submitting crafted files or input data that triggers the vulnerable code path during regular expression matching operations. The vulnerability's remote exploitability means that systems processing untrusted input through PCRE functions are at risk, potentially affecting web applications, network security appliances, and any software that incorporates PCRE for text processing. This vulnerability directly aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter: Python and T1499.004 for Network Denial of Service, as it enables both service disruption and potential system compromise through memory corruption attacks.
Mitigation strategies for CVE-2017-7245 primarily involve immediate patching of affected systems with updated PCRE library versions that contain the necessary code fixes. Organizations should prioritize updating their PCRE installations to versions that have addressed this buffer overflow vulnerability, typically those released after the vulnerability disclosure. Additionally, implementing input validation and sanitization measures can help reduce the attack surface by filtering potentially malicious input before it reaches the regular expression processing functions. System administrators should also consider implementing network segmentation and access controls to limit the potential impact of exploitation attempts. The vulnerability highlights the importance of regular security updates and proper memory management practices in software development, particularly for libraries that handle untrusted input data. Organizations should conduct comprehensive vulnerability assessments to identify all systems using affected PCRE versions and establish monitoring procedures to detect potential exploitation attempts. This vulnerability underscores the necessity of following secure coding practices and adhering to industry standards such as those defined by the CWE and MITRE ATT&CK frameworks for preventing similar memory safety issues in future software development cycles.