CVE-2011-1487 in Perl
Summary
by MITRE
The (1) lc, (2) lcfirst, (3) uc, and (4) ucfirst functions in Perl 5.10.x, 5.11.x, and 5.12.x through 5.12.3, and 5.13.x through 5.13.11, do not apply the taint attribute to the return value upon processing tainted input, which might allow context-dependent attackers to bypass the taint protection mechanism via a crafted string.
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Analysis
by VulDB Data Team • 09/23/2024
The vulnerability described in CVE-2011-1487 represents a critical flaw in Perl's text processing functions that directly undermines the language's taint checking security mechanism. This issue affects multiple Perl versions including 5.10.x, 5.11.x, 5.12.x through 5.12.3, and 5.13.x through 5.13.11, making it a widespread concern across several major Perl releases. The flaw specifically targets four fundamental string manipulation functions: lc, lcfirst, uc, and ucfirst which are commonly used throughout Perl applications for text transformation tasks.
The technical nature of this vulnerability lies in the improper handling of taint attributes during string processing operations. When Perl processes tainted input through these functions, the taint attribute should be preserved in the returned value to maintain the security context that prevents untrusted data from being used in potentially dangerous operations. However, these functions fail to propagate the taint attribute from input to output, effectively creating a bypass mechanism that allows attackers to circumvent Perl's built-in security protections. This behavior creates a situation where tainted data can be processed through these functions and subsequently used in contexts where taint checking would normally prevent execution.
The operational impact of this vulnerability is significant as it enables context-dependent attackers to bypass taint protection mechanisms that are designed to prevent code injection attacks and other security exploits. Attackers can craft malicious input strings that, when processed through these functions, will appear untainted to subsequent security checks. This weakness particularly affects applications that rely on Perl's taint mode for security, where the language's built-in protections are expected to prevent dangerous operations on untrusted input. The vulnerability essentially allows attackers to create a false sense of security by manipulating the taint state of data during processing operations.
This vulnerability maps to CWE-174, which specifically addresses the issue of insufficient taint checking in programming languages, and aligns with ATT&CK technique T1059.007 for script-based execution. The flaw represents a classic example of how security mechanisms can be undermined through seemingly benign function behavior, particularly affecting applications that depend on taint checking for security boundaries. Organizations using affected Perl versions should prioritize immediate patching or implementation of compensating controls, as the vulnerability can be exploited to bypass multiple security layers that depend on proper taint attribute handling. The issue demonstrates the critical importance of maintaining proper security state propagation in language-level functions that handle user input, as failures in this area can compromise entire application security models.