CVE-2016-7416 in macOS
Summary
by MITRE
ext/intl/msgformat/msgformat_format.c in PHP before 5.6.26 and 7.x before 7.0.11 does not properly restrict the locale length provided to the Locale class in the ICU library, which allows remote attackers to cause a denial of service (application crash) or possibly have unspecified other impact via a MessageFormatter::formatMessage call with a long first argument.
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Analysis
by VulDB Data Team • 10/07/2022
The vulnerability identified as CVE-2016-7416 affects PHP versions prior to 5.6.26 and 7.0.11, specifically within the internationalization extension's message formatting component. This issue resides in the ext/intl/msgformat/msgformat_format.c file where the MessageFormatter class fails to properly validate or restrict the length of locale identifiers passed to the underlying ICU library. The flaw represents a classic buffer overflow condition that can be exploited through improper input validation, creating a potential denial of service condition that may result in application crashes.
The technical implementation of this vulnerability stems from the MessageFormatter::formatMessage method's handling of locale parameters without adequate bounds checking. When a maliciously crafted long locale string is passed to this function, the ICU library's Locale class processes the input without proper length restrictions, potentially leading to memory corruption. This behavior aligns with CWE-122, which describes insufficient restriction of operations within the bounds of a memory buffer, and can be categorized under CWE-400 as an unspecified other impact that may include arbitrary code execution or information disclosure depending on exploitation circumstances.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more sophisticated attacks. Remote attackers can leverage this weakness to crash PHP applications that utilize the MessageFormatter functionality, effectively causing service disruption for legitimate users. The vulnerability's exploitation requires only a single call to MessageFormatter::formatMessage with a specially crafted long first argument, making it particularly dangerous as it can be triggered through web-based interfaces without requiring special privileges or complex attack chains. This characteristic places the vulnerability in the ATT&CK framework under T1499.004 for Network Denial of Service and potentially T1059.007 for Command and Scripting Interpreter.
Mitigation strategies for CVE-2016-7416 primarily involve upgrading PHP installations to versions 5.6.26 or 7.0.11 and later, which contain the necessary patches to properly validate locale parameter lengths. Organizations should also implement input validation measures at the application level, ensuring that all locale identifiers passed to MessageFormatter functions are strictly bounded and sanitized before processing. Additional protective measures include deploying web application firewalls that can detect and block suspicious parameter patterns, implementing proper error handling to prevent crash propagation, and monitoring application logs for unusual patterns that may indicate exploitation attempts. The vulnerability highlights the importance of proper input validation in internationalization libraries and demonstrates how seemingly benign parameter handling can create significant security risks when combined with underlying library behaviors that do not adequately protect against buffer overflows.