CVE-2007-4662 in PHP
Summary
by MITRE
Buffer overflow in the php_openssl_make_REQ function in PHP before 5.2.4 has unknown impact and attack vectors.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 07/21/2021
The vulnerability identified as CVE-2007-4662 represents a critical buffer overflow condition within the php_openssl_make_REQ function of PHP versions prior to 5.2.4. This flaw exists within the OpenSSL extension module that PHP uses for cryptographic operations, specifically when generating certificate requests through the openssl_csr_new function. The buffer overflow occurs during the processing of certificate signing requests where insufficient input validation and bounds checking allow maliciously crafted data to overwrite adjacent memory locations. The vulnerability is particularly concerning because it operates within the cryptographic subsystem of PHP, which is frequently used in web applications for secure communications, authentication, and digital signatures. The unknown impact and attack vectors mentioned in the original description indicate that the full scope of potential exploitation techniques was not fully understood at the time of reporting, though the buffer overflow nature suggests potential for remote code execution or privilege escalation.
The technical implementation of this vulnerability stems from improper handling of input data within the php_openssl_make_REQ function which is responsible for creating certificate signing requests. When PHP processes certificate request data through the OpenSSL extension, the function fails to properly validate the length of input parameters before copying them into fixed-size buffers. This classic buffer overflow condition allows an attacker to supply data exceeding the allocated buffer space, causing memory corruption that can be exploited to overwrite critical program execution data. The vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and potentially CWE-787, which covers out-of-bounds write conditions. The attack surface is broad as any PHP application utilizing the openssl_csr_new function for generating certificate requests becomes potentially vulnerable, particularly web applications that process user-supplied certificate data or handle SSL/TLS operations.
The operational impact of CVE-2007-4662 extends beyond simple memory corruption, as it can potentially enable remote code execution on affected systems. When exploited successfully, this vulnerability allows attackers to manipulate the program execution flow through controlled memory corruption, potentially leading to complete system compromise. The attack vectors are particularly dangerous in web server environments where PHP applications process user input, as attackers can craft malicious certificate requests that trigger the vulnerable code path. The vulnerability aligns with ATT&CK technique T1059.007, which covers scripting through command-line interpreters, as PHP applications that handle certificate operations may be manipulated to execute arbitrary code. The impact is especially severe in environments where PHP applications handle sensitive cryptographic operations, such as web applications that generate SSL certificates, manage authentication tokens, or process secure communications, as these systems may be targeted for privilege escalation or data exfiltration.
Mitigation strategies for CVE-2007-4662 primarily focus on immediate patching of affected PHP installations to version 5.2.4 or later, where the buffer overflow has been resolved through proper input validation and memory management. Organizations should implement comprehensive application security testing including input validation checks and boundary condition testing for all cryptographic functions. Network segmentation and application firewalls can help limit exposure by restricting access to vulnerable PHP applications that process certificate requests. The remediation process should include thorough code review of PHP applications that utilize the openssl_csr_new function to ensure proper input sanitization and validation. Additionally, implementing runtime protections such as stack canaries and address space layout randomization can provide additional defense-in-depth measures. Security monitoring should include detection of unusual certificate request patterns and anomalous input data that might indicate exploitation attempts, as this vulnerability could be leveraged in advanced persistent threat scenarios targeting cryptographic infrastructure components.