CVE-2016-5769 in macOS
Summary
by MITRE
Multiple integer overflows in mcrypt.c in the mcrypt extension in PHP before 5.5.37, 5.6.x before 5.6.23, and 7.x before 7.0.8 allow remote attackers to cause a denial of service (heap-based buffer overflow and application crash) or possibly have unspecified other impact via a crafted length value, related to the (1) mcrypt_generic and (2) mdecrypt_generic functions.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-5769 represents a critical security flaw within the mcrypt extension of PHP, affecting versions prior to specific patched releases. This issue manifests through integer overflow conditions that can be exploited remotely to trigger heap-based buffer overflows and application crashes. The vulnerability specifically impacts the mcrypt_generic and mdecrypt_generic functions, which are fundamental components for cryptographic operations within PHP applications. The flaw arises from improper handling of length parameters during cryptographic processing, creating opportunities for attackers to manipulate memory allocation and execution flow.
The technical implementation of this vulnerability stems from inadequate input validation within the mcrypt.c source file where integer overflows occur during the calculation of buffer sizes for cryptographic operations. When attackers provide crafted length values, the integer overflow conditions cause the system to allocate insufficient memory buffers or calculate incorrect memory offsets. This leads to heap corruption that can result in application crashes or potentially more severe consequences including arbitrary code execution. The vulnerability operates at the intersection of memory safety and cryptographic implementation, making it particularly dangerous in web applications that rely heavily on PHP's encryption capabilities.
From an operational perspective, this vulnerability presents significant risk to web applications and servers running affected PHP versions. The remote exploitation capability means that attackers can potentially compromise systems without requiring local access or authentication. The denial of service impact can disrupt legitimate service availability, while the potential for unspecified other impacts suggests the possibility of more severe consequences including privilege escalation or data compromise. Organizations running PHP applications that utilize mcrypt functions for encryption, decryption, or cryptographic operations face substantial risk if they have not applied the relevant patches. The vulnerability affects multiple PHP version streams simultaneously, indicating a widespread impact across different PHP release channels.
The security implications of CVE-2016-5769 align with common weakness enumerations such as CWE-190, which describes integer overflow conditions, and CWE-121, which covers stack-based buffer overflow scenarios. The attack pattern follows established methodologies from the ATT&CK framework under the T1499 category for network denial of service, with potential progression to T1059 for command execution if the vulnerability allows for code injection. The vulnerability's impact extends beyond immediate service disruption to encompass potential data integrity concerns, particularly in applications where mcrypt functions handle sensitive information such as user credentials, session tokens, or encrypted communications. Organizations should prioritize patching affected systems and consider implementing additional monitoring for anomalous memory allocation patterns or application crashes that may indicate exploitation attempts.
Mitigation strategies for this vulnerability require immediate application of the security patches released by the PHP development team for the affected versions. System administrators should conduct comprehensive inventory assessments to identify all affected PHP installations across their infrastructure and apply updates promptly. Additionally, implementing network monitoring solutions that can detect unusual memory allocation patterns or application behavior may provide early warning of potential exploitation attempts. The vulnerability highlights the importance of maintaining up-to-date cryptographic libraries and extensions, as well as the need for regular security assessments of PHP applications. Organizations should also consider migrating away from the deprecated mcrypt extension to more modern and actively maintained cryptographic libraries such as OpenSSL or libsodium to reduce exposure to similar vulnerabilities in the future.