CVE-2016-7412 in macOS
Summary
by MITRE
ext/mysqlnd/mysqlnd_wireprotocol.c in PHP before 5.6.26 and 7.x before 7.0.11 does not verify that a BIT field has the UNSIGNED_FLAG flag, which allows remote MySQL servers to cause a denial of service (heap-based buffer overflow) or possibly have unspecified other impact via crafted field metadata.
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Analysis
by VulDB Data Team • 10/07/2022
The vulnerability identified as CVE-2016-7412 represents a critical heap-based buffer overflow in PHP's mysqlnd extension that affects versions prior to 5.6.26 and 7.0.11. This issue resides within the mysqlnd_wireprotocol.c file and specifically targets the handling of BIT field metadata during MySQL database communications. The flaw occurs when PHP processes field metadata from remote MySQL servers without properly validating whether a BIT field contains the UNSIGNED_FLAG flag, creating a potential attack vector that could be exploited by malicious database servers.
The technical implementation of this vulnerability stems from insufficient input validation within the MySQL protocol handling layer of PHP's mysqlnd extension. When PHP receives field metadata from a MySQL server, it expects certain flag patterns to validate data types properly. However, the mysqlnd component fails to verify that BIT fields correctly implement the UNSIGNED_FLAG, which is a standard flag used in MySQL protocol specifications to indicate unsigned integer types. This missing validation creates a scenario where a malicious MySQL server can craft field metadata that causes PHP's memory management system to attempt operations beyond allocated buffer boundaries, resulting in heap corruption and potential denial of service conditions.
From an operational impact perspective, this vulnerability presents significant security implications for PHP applications that connect to remote MySQL databases. The potential for remote code execution exists through the buffer overflow, as attackers could craft malicious field metadata that, when processed by vulnerable PHP applications, could lead to arbitrary code execution on the affected system. Additionally, the vulnerability enables denial of service attacks that could crash PHP processes and render web applications unavailable to legitimate users. The unspecified other impacts mentioned in the CVE description suggest that beyond the immediate buffer overflow, there may be additional security implications related to memory corruption that could be leveraged for more sophisticated attacks.
The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and demonstrates how improper input validation can lead to memory corruption vulnerabilities. From an attacker's perspective, this issue maps to ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation could allow attackers to execute arbitrary commands on the affected system. The attack surface is particularly concerning for web applications that use PHP to interact with MySQL databases, as the vulnerability can be exploited through database connection parameters without requiring additional authentication or privileges.
Organizations should immediately implement mitigations by upgrading to PHP versions 5.6.26 or 7.0.11, which contain the necessary patches to validate BIT field metadata properly. Network segmentation and database server hardening measures can provide additional protection layers while waiting for patches to be deployed. Monitoring for unusual database connection patterns and implementing proper input validation at application level can help detect potential exploitation attempts. Security teams should also consider implementing intrusion detection systems that can identify malicious field metadata patterns that might indicate exploitation attempts against this vulnerability. The patch addresses the root cause by implementing proper flag validation in the mysqlnd extension, ensuring that all BIT field metadata is properly verified before processing, thereby preventing the heap-based buffer overflow condition that could lead to system compromise.