CVE-2016-4071 in Mac OS X
Summary
by MITRE
Format string vulnerability in the php_snmp_error function in ext/snmp/snmp.c in PHP before 5.5.34, 5.6.x before 5.6.20, and 7.x before 7.0.5 allows remote attackers to execute arbitrary code via format string specifiers in an SNMP::get call.
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Analysis
by VulDB Data Team • 01/19/2025
The CVE-2016-4071 vulnerability represents a critical format string vulnerability within PHP's SNMP extension that affects multiple versions of the PHP runtime environment. This flaw exists in the php_snmp_error function located in the ext/snmp/snmp.c file, where improper handling of user-supplied input during SNMP operations creates a pathway for remote code execution. The vulnerability specifically manifests when the SNMP::get method processes format string specifiers, allowing attackers to manipulate the function's behavior through crafted input parameters that are subsequently interpreted as format specifiers rather than literal data.
The technical exploitation of this vulnerability leverages the fundamental weakness in how PHP processes format strings within its SNMP extension. When an SNMP::get call is made with maliciously crafted input, the php_snmp_error function fails to properly sanitize or escape the input before passing it to underlying SNMP library functions. This creates a classic format string vulnerability where attacker-controlled data can contain format specifiers such as %s, %d, or %x that are interpreted by the printf-family functions, potentially leading to stack corruption, information disclosure, or arbitrary code execution. The vulnerability operates at the intersection of improper input validation and insecure coding practices in the SNMP extension's error handling mechanisms.
The operational impact of this vulnerability extends beyond simple remote code execution to encompass potential system compromise and data breach scenarios. Attackers can exploit this vulnerability to execute arbitrary code on systems running affected PHP versions, potentially gaining full control over web servers or application environments. The vulnerability affects PHP installations across multiple version lines including 5.5.x, 5.6.x, and 7.x, making it particularly dangerous as it impacts a wide range of web applications and server configurations. The remote nature of the attack means that exploitation can occur without requiring local system access, making it a significant threat to web server security and application integrity.
Security practitioners should implement immediate mitigations including updating to patched PHP versions where available, as the vulnerability affects versions prior to PHP 5.5.34, 5.6.20, and 7.0.5. Organizations should also consider implementing network-level restrictions and input validation controls to limit the exposure of SNMP functionality to untrusted inputs. The vulnerability aligns with CWE-134, which specifically addresses format string vulnerabilities, and represents a significant risk under ATT&CK framework's execution and privilege escalation techniques. Additionally, the vulnerability demonstrates the importance of proper input sanitization and secure coding practices, particularly when dealing with extension modules that interface with external libraries and protocols.