CVE-2016-2381 in Communications Billing
Summary
by MITRE
Perl might allow context-dependent attackers to bypass the taint protection mechanism in a child process via duplicate environment variables in envp.
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Analysis
by VulDB Data Team • 01/17/2021
The vulnerability identified as CVE-2016-2381 represents a critical security flaw in the Perl programming language that undermines the fundamental taint protection mechanism designed to prevent dangerous operations. This weakness specifically affects how Perl handles environment variables when executing child processes, creating a potential pathway for context-dependent attackers to circumvent security controls that are meant to protect against malicious input manipulation.
The technical flaw resides in Perl's implementation of the execve system call when processing environment variables through the envp parameter. When Perl duplicates environment variables for child processes, it fails to properly handle cases where duplicate variable names exist within the environment array. This improper handling allows attackers to inject malicious values that can bypass the taint checking mechanisms that Perl employs to validate data before it can be used in potentially dangerous operations such as system calls or file operations.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally compromises the security model that Perl developers rely upon for protecting against code injection attacks. Attackers can exploit this weakness by crafting environment variable sets that contain duplicate entries, where the second occurrence of a variable name can override or bypass taint checking in ways that were not intended by the language's security design. This creates a scenario where tainted data can flow through the system without proper validation, potentially leading to arbitrary code execution or data compromise.
This vulnerability maps directly to CWE-254 in the Common Weakness Enumeration catalog, which specifically addresses "Security Features" and the improper handling of security-sensitive data. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the T1059.007 sub-technique for "Command and Scripting Interpreter: PowerShell" and T1127.001 for "Command and Scripting Interpreter: Visual Basic', though it specifically targets the underlying environment variable handling mechanism. The flaw demonstrates a classic case of inadequate input validation in a security-critical context where environment variables serve as a bridge between untrusted input and system execution.
Mitigation strategies for CVE-2016-2381 require immediate patching of affected Perl installations to versions that properly handle duplicate environment variables during process execution. System administrators should also implement monitoring for unusual environment variable patterns and consider implementing additional security controls such as environment variable sanitization routines that validate and normalize environment data before process execution. Organizations should conduct comprehensive security reviews of their Perl-based applications to identify any code patterns that might be vulnerable to this class of attack, particularly those that rely heavily on environment variable manipulation or execute external commands based on environment data. Additionally, implementing proper privilege separation and using restricted execution environments can help limit the impact should an attacker successfully exploit this vulnerability.