CVE-2017-12814 in Perl
Summary
by MITRE
Stack-based buffer overflow in the CPerlHost::Add method in win32/perlhost.h in Perl before 5.24.3-RC1 and 5.26.x before 5.26.1-RC1 on Windows allows attackers to execute arbitrary code via a long environment variable.
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Analysis
by VulDB Data Team • 01/14/2021
The vulnerability identified as CVE-2017-12814 represents a critical stack-based buffer overflow flaw within the Perl interpreter's Windows implementation. This issue specifically affects the CPerlHost::Add method located in the win32/perlhost.h file, which serves as a crucial component for Perl's Windows host integration. The vulnerability arises from inadequate input validation when processing environment variables, creating a scenario where attackers can manipulate the program's execution flow through carefully crafted malicious input. The flaw exists in Perl versions prior to 5.24.3-RC1 and 5.26.x versions before 5.26.1-RC1, making a substantial portion of the Perl user base vulnerable to exploitation.
The technical nature of this vulnerability stems from a classic stack buffer overflow condition where the CPerlHost::Add method fails to properly bounds-check the length of environment variable values before copying them into fixed-size stack buffers. When an attacker provides an environment variable containing excessive data, the overflow occurs as the program attempts to store the oversized input beyond the allocated buffer boundaries. This condition corrupts adjacent stack memory, potentially allowing an attacker to overwrite return addresses, function pointers, or other critical program state information. The vulnerability maps directly to CWE-121 Stack-based Buffer Overflow, which is categorized under the Common Weakness Enumeration framework as a fundamental memory safety issue that enables arbitrary code execution.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with a pathway to compromise systems running vulnerable Perl installations. Attackers can leverage this flaw to execute malicious code with the privileges of the affected process, typically resulting in system compromise, data theft, or further lateral movement within network environments. The vulnerability is particularly concerning in server environments where Perl applications process untrusted input from environment variables, as it can be exploited through various attack vectors including web applications, system administration tools, or automated scripts that rely on environment variable processing. The attack requires minimal privileges and can be executed remotely, making it a significant threat to system security.
Mitigation strategies for CVE-2017-12814 primarily focus on immediate patching of affected Perl installations to versions 5.24.3-RC1 or later and 5.26.1-RC1 or later, which contain the necessary fixes to prevent the buffer overflow condition. System administrators should also implement environment variable validation controls to limit the size and content of environment variables processed by Perl applications. Additional defensive measures include deploying application whitelisting solutions, restricting environment variable modifications, and implementing runtime protections such as stack canaries or address space layout randomization. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as T1059 Command and Scripting Interpreter and T1068 Exploitation for Privilege Escalation, demonstrating how buffer overflow vulnerabilities can serve as initial access vectors for more sophisticated attacks. Organizations should also consider monitoring for unusual environment variable patterns and implementing comprehensive vulnerability management processes to prevent similar issues in other components of their software stack.