Arbitrary code execution vulnerability (CVE-2019-6977) affects the PHP GD image processing library in PHP versions 4 through 7.3. The vulnerability is caused by insufficient input validation in the gdImageCreateFromGd2() function that could allow an attacker to execute arbitrary code on the affected system.
When an attacker sends a specially crafted GD2 image file to a vulnerable PHP application that uses the gdImageCreateFromGd2() function, the flaw can be triggered. An attacker can exploit the vulnerability by creating a malicious GD2 image file that contains malicious code in the form of PHP commands. Once the file is processed by the vulnerable application, the attacker's code will be executed with the permissions of the web server user.
To mitigate this vulnerability, it is recommended to update to the latest version of PHP, as the flaw has been patched in PHP 7.3.1 and later versions. If upgrading is not possible, disabling the gdImageCreateFromGd2() function or restricting access to the function through proper input validation can help prevent exploitation of this vulnerability. Additionally, implementing other security measures such as input validation and output sanitization can help reduce the risk of exploitation of similar vulnerabilities in the future.
When an attacker sends a specially crafted GD2 image file to a vulnerable PHP application that uses the gdImageCreateFromGd2() function, the flaw can be triggered. An attacker can exploit the vulnerability by creating a malicious GD2 image file that contains malicious code in the form of PHP commands. Once the file is processed by the vulnerable application, the attacker's code will be executed with the permissions of the web server user.
To mitigate this vulnerability, it is recommended to update to the latest version of PHP, as the flaw has been patched in PHP 7.3.1 and later versions. If upgrading is not possible, disabling the gdImageCreateFromGd2() function or restricting access to the function through proper input validation can help prevent exploitation of this vulnerability. Additionally, implementing other security measures such as input validation and output sanitization can help reduce the risk of exploitation of similar vulnerabilities in the future.