CVE-2020-14155 in HTTP Server
Summary
by MITRE
libpcre in PCRE before 8.44 allows an integer overflow via a large number after a (?C substring.
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Analysis
by VulDB Data Team • 11/16/2022
The vulnerability CVE-2020-14155 represents a critical integer overflow flaw within the PCRE (Perl Compatible Regular Expressions) library version 8.43 and earlier. This issue specifically manifests when processing regular expressions containing a large number following a (?C substring, which is a conditional construct in PCRE syntax. The vulnerability stems from insufficient input validation and arithmetic overflow handling within the library's parsing routines. The integer overflow occurs during the processing of conditional assertions, where the library fails to properly validate the size of numeric values that follow the (?C construct, leading to unpredictable behavior and potential system compromise.
The technical implementation of this vulnerability involves the library's handling of conditional assertions in regular expressions, where the (?C substring serves as a conditional construct that can contain numeric values. When these numeric values exceed the maximum representable integer value for the system architecture, the arithmetic operations trigger integer overflow conditions. This overflow can cause the library to allocate insufficient memory or perform invalid memory operations, creating opportunities for exploitation. The flaw is particularly dangerous because it can be triggered through user-supplied regular expressions, making it applicable to any application that relies on PCRE for pattern matching operations. This vulnerability directly maps to CWE-190, which describes integer overflow conditions, and aligns with ATT&CK technique T1059.007 for execution through command and scripting interpreters, as the overflow could potentially be exploited to manipulate program execution flow.
The operational impact of CVE-2020-14155 extends across numerous applications and systems that utilize the PCRE library for text processing, pattern matching, or security filtering operations. Systems vulnerable to this flaw include web applications, network intrusion detection systems, log analysis tools, and any software that processes user-provided regular expressions. The integer overflow can result in denial of service conditions where applications crash or become unresponsive, or more critically, could enable arbitrary code execution under certain circumstances. Attackers could potentially leverage this vulnerability to bypass security controls, manipulate application behavior, or escalate privileges within affected systems. The widespread adoption of PCRE across various software platforms amplifies the potential scope of impact, as many security tools and applications depend on this library for their regular expression processing capabilities.
Mitigation strategies for CVE-2020-14155 focus primarily on upgrading to PCRE version 8.44 or later, which includes patches addressing the integer overflow condition. Organizations should conduct comprehensive vulnerability assessments to identify all systems utilizing vulnerable PCRE versions and prioritize remediation efforts accordingly. Additionally, implementing input validation measures that restrict the size and complexity of regular expressions processed by applications can provide additional defense-in-depth. Security teams should monitor for exploitation attempts through network traffic analysis, log monitoring, and application behavior analysis. The patch implementation should be accompanied by thorough regression testing to ensure that the updated library does not introduce compatibility issues with existing applications. Organizations should also consider implementing runtime protections such as address space layout randomization and stack canaries to mitigate potential exploitation attempts, while maintaining updated threat intelligence feeds to track emerging exploitation patterns targeting this vulnerability.