CVE-2019-11041 Explained : Impact and Mitigation

PHP versions 7.1.x below 7.1.31, 7.2.x below 7.2.21, and 7.3.x below 7.3.8 are affected by a vulnerability in the PHP EXIF extension that can lead to information disclosure or system crashes.

Understanding CVE-2019-11041

This CVE involves a heap-buffer-overflow on exif_scan_thumbnail in the EXIF extension of PHP.

What is CVE-2019-11041?

In PHP versions 7.1.x below 7.1.31, 7.2.x below 7.2.21, and 7.3.x below 7.3.8, a vulnerability in the PHP EXIF extension allows attackers to exceed buffer size limits when parsing EXIF data, potentially leading to sensitive data exposure or system instability.

The Impact of CVE-2019-11041

The vulnerability has a CVSS base score of 4.8 (Medium severity) with a HIGH attack complexity. While the confidentiality impact is low, the availability impact is also low, and integrity impact is none.

Technical Details of CVE-2019-11041

This section provides more in-depth technical information about the CVE.

Vulnerability Description

The issue arises when the PHP EXIF extension processes EXIF data from images, such as through the exif_read_data() function, allowing data to extend beyond allocated buffers, potentially causing a heap buffer overflow.

Affected Systems and Versions

PHP 7.1.x versions below 7.1.31
PHP 7.2.x versions below 7.2.21
PHP 7.3.x versions below 7.3.8

Exploitation Mechanism

Attackers can exploit this vulnerability by providing malicious data to functions like exif_read_data(), causing the PHP EXIF extension to read past the allocated buffer size.

Mitigation and Prevention

Protecting systems from CVE-2019-11041 requires immediate actions and long-term security practices.

Immediate Steps to Take

Update PHP to versions 7.1.31, 7.2.21, or 7.3.8 to mitigate the vulnerability.
Monitor for any unusual activities that could indicate exploitation of the vulnerability.

Long-Term Security Practices

Regularly update PHP and other software to the latest versions to patch known vulnerabilities.
Implement secure coding practices to prevent buffer overflows and other common vulnerabilities.

Patching and Updates

Apply patches provided by PHP Group to address the heap-buffer-overflow vulnerability in the EXIF extension.