CVE-2011-1467 in PHP
Summary
by MITRE
Unspecified vulnerability in the NumberFormatter::setSymbol (aka numfmt_set_symbol) function in the Intl extension in PHP before 5.3.6 allows context-dependent attackers to cause a denial of service (application crash) via an invalid argument, a related issue to CVE-2010-4409.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2011-1467 resides within the NumberFormatter::setSymbol function of PHP's Intl extension, a critical component that handles internationalization and localization tasks. This flaw affects PHP versions prior to 5.3.6 and represents a context-dependent denial of service vulnerability that can be exploited by remote attackers. The issue stems from inadequate input validation within the numfmt_set_symbol function, which processes symbolic representations of numbers such as currency symbols, decimal separators, and grouping separators. When malformed or invalid arguments are passed to this function, the application experiences unexpected behavior leading to complete crash conditions.
The technical implementation of this vulnerability involves the improper handling of input parameters within the Intl extension's number formatting subsystem. The NumberFormatter::setSymbol function is designed to configure various formatting symbols for numeric values, but lacks robust boundary checking and parameter validation mechanisms. Attackers can craft malicious inputs that trigger buffer overflows, memory corruption, or invalid memory access patterns within the underlying ICU (International Components for Unicode) library that PHP's Intl extension relies upon. This vulnerability operates at the application level and can be classified under CWE-121 as a stack-based buffer overflow or CWE-122 as heap-based buffer overflow depending on the specific execution context. The flaw demonstrates characteristics consistent with the ATT&CK technique T1499.004 which involves network denial of service attacks through application layer vulnerabilities.
The operational impact of CVE-2011-1467 extends beyond simple service disruption to potentially compromise entire web applications that depend on PHP's internationalization capabilities. When exploited, this vulnerability can cause web servers to crash repeatedly, leading to extended downtime and service unavailability for legitimate users. The context-dependent nature of the vulnerability means that exploitation requires specific conditions related to how the NumberFormatter::setSymbol function is invoked within applications, making it particularly dangerous in environments where user input flows directly into internationalization functions. Applications utilizing PHP's Intl extension for currency display, number formatting, or localization features are at risk, particularly those handling untrusted input from web forms or API endpoints. The vulnerability creates a persistent threat that can be leveraged for sustained denial of service attacks against web applications, with potential cascading effects on server resources and overall system availability.
Mitigation strategies for CVE-2011-1467 primarily focus on immediate version upgrades to PHP 5.3.6 or later, which incorporates patches addressing the input validation deficiencies in the NumberFormatter::setSymbol function. Organizations should implement comprehensive patch management procedures to ensure all PHP installations are updated promptly, particularly in production environments where the vulnerability could be exploited. Additionally, developers should sanitize all inputs before passing them to internationalization functions, implement proper error handling mechanisms, and consider using input validation libraries or frameworks that provide additional layers of protection. The vulnerability aligns with ATT&CK tactic T1595 which involves reconnaissance activities to identify system vulnerabilities, and defensive measures should include network monitoring for suspicious patterns of service disruption. Organizations should also consider implementing application firewalls or web application security controls that can detect and block malicious requests targeting known vulnerable functions within PHP applications. Regular security audits and code reviews focusing on internationalization functions can help identify similar vulnerabilities before they can be exploited by threat actors.