CVE-2011-2201 in Data::FormValidator
Summary
by MITRE
The Data::FormValidator module 4.66 and earlier for Perl, when untaint_all_constraints is enabled, does not properly preserve the taint attribute of data, which might allow remote attackers to bypass the taint protection mechanism via form input.
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Analysis
by VulDB Data Team • 09/26/2024
The Data::FormValidator module vulnerability CVE-2011-2201 represents a critical flaw in Perl application security that directly undermines taint checking mechanisms designed to prevent injection attacks. This vulnerability affects versions 4.66 and earlier of the Data::FormValidator Perl module, which is widely used for validating form input in web applications. The issue specifically manifests when the untaint_all_constraints configuration option is enabled, creating a pathway for malicious actors to circumvent security protections that should prevent untrusted data from being processed in dangerous contexts.
The technical flaw resides in how the module handles data taint attributes during validation processes. When untaint_all_constraints is activated, the module fails to properly maintain the taint status of input data, allowing tainted values to be treated as safe. This occurs because the validation process does not adequately preserve the taint flag that Perl uses to mark data as potentially untrusted. The vulnerability creates a scenario where attackers can craft form inputs that bypass taint checking, effectively neutralizing the security protections that should prevent malicious data from being executed or processed in sensitive operations. This behavior directly violates the fundamental principles of secure programming where tainted data must remain tainted throughout processing until explicitly untainted through proper validation.
The operational impact of this vulnerability extends beyond simple data validation failures, as it enables attackers to bypass critical security controls that protect against code injection, command execution, and other malicious activities. When applications rely on taint checking to prevent dangerous operations with user input, this vulnerability creates a backdoor that allows attackers to inject malicious content that would normally be blocked. The implications are particularly severe in web applications where form data is processed and potentially executed, as the vulnerability could enable attackers to perform actions such as arbitrary code execution, data manipulation, or privilege escalation depending on how the validated data is subsequently used. This represents a significant weakening of the application's security posture and violates the principle of least privilege that should govern all security-sensitive operations.
Organizations affected by this vulnerability should prioritize immediate remediation through module updates to versions that address the taint attribute preservation issue. The recommended mitigation involves upgrading to Data::FormValidator version 4.67 or later where the taint handling has been corrected to properly maintain data taint attributes throughout the validation process. Security teams should also conduct thorough code reviews to identify any instances where the untaint_all_constraints option is enabled and assess the potential impact on existing security controls. Additionally, implementing additional input validation layers and monitoring for suspicious form data patterns can provide defense-in-depth protection while waiting for full patch deployment. This vulnerability aligns with CWE-20, which addresses improper input validation, and represents a specific case of CWE-116, improper handling of taint attributes, making it particularly relevant to the ATT&CK framework's defense evasion techniques where attackers leverage application flaws to bypass security controls.