CVE-2018-18312 in Perl
Summary
by MITRE
Perl before 5.26.3 and 5.28.0 before 5.28.1 has a buffer overflow via a crafted regular expression that triggers invalid write operations.
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Analysis
by VulDB Data Team • 04/16/2020
This vulnerability exists in perl versions prior to 5.26.3 and 5.28.1, representing a critical buffer overflow flaw that can be exploited through maliciously crafted regular expressions. The issue stems from inadequate input validation within perl's regular expression engine, specifically when processing complex pattern matching operations that exceed allocated memory boundaries. This vulnerability falls under the CWE-121 buffer overflow category, where insufficient bounds checking allows attackers to write data beyond the allocated buffer space, potentially leading to arbitrary code execution or system compromise.
The technical exploitation occurs when perl processes regular expressions containing crafted sequences that trigger invalid write operations during pattern compilation or execution phases. Attackers can construct malicious regex patterns that cause the interpreter to allocate insufficient memory for internal data structures while simultaneously attempting to write beyond these boundaries. This flaw is particularly dangerous because perl is widely used in web applications, system administration scripts, and network security tools, making it a prime target for remote code execution attacks. The vulnerability operates at the core level of perl's string handling and pattern matching capabilities, which are fundamental to the language's functionality.
The operational impact of this vulnerability extends across numerous attack vectors where perl scripts process untrusted input through regular expressions. Systems running vulnerable perl versions are susceptible to remote code execution when processing user-supplied data in web applications, network services, or automated security tools that rely on perl for text processing. The attack surface includes web servers executing perl CGI scripts, network security appliances, intrusion detection systems, and various automation tools that utilize perl's regex capabilities. This vulnerability can be leveraged by attackers to gain unauthorized access to systems, escalate privileges, or cause denial of service conditions.
Mitigation strategies for this vulnerability primarily involve upgrading to perl versions 5.26.3 or 5.28.1 and later, which contain the necessary patches to address the buffer overflow conditions. Organizations should conduct comprehensive inventory audits to identify all systems running vulnerable perl versions and prioritize updates accordingly. Additionally, implementing input validation controls and sanitization measures can provide defensive layers against exploitation attempts. Security teams should monitor for any attempts to exploit this vulnerability through network traffic analysis and log monitoring. The ATT&CK framework categorizes this as a code injection technique under the T1059.007 sub-technique, emphasizing the need for proper input validation and secure coding practices. Organizations should also consider implementing runtime protections and application whitelisting to prevent execution of untrusted perl scripts that might be vulnerable to this class of attack.