CVE-2018-17082 Scanner

Apache2 PHP is widely used by developers around the world to create dynamic content for websites and web applications. The software is responsible for handling server-side scripting operations in PHP, functioning as an essential component within the Apache web server. This integration facilitates seamless server-client communications, allowing developers to implement custom functionalities efficiently. Apache2 PHP is a critical tool in web hosting environments, providing a robust platform for web development and deployment. Organizations rely on its flexibility and extensive support for multiple operating systems to power their digital presence. Apache2 PHP's popularity stems largely from its open-source nature, encouraging community collaboration and continuous improvement.

The Cross-Site Scripting (XSS) vulnerability in Apache2 PHP is caused by improper handling of chunked transfer-encoding requests. This vulnerability allows an attacker to execute arbitrary scripts in the context of the affected server. By leveraging this flaw, attackers may perform multiple malicious actions, including session hijacking and data theft. Reflected XSS attacks can exploit this vulnerability, potentially undermining user trust and leading to privacy violations. The impact scope extends to any web application using vulnerable versions of PHP, particularly those integrated with Apache2 PHP. Mitigation of this issue requires an understanding of both transfer-encoding mechanisms and the underlying script injection vectors.

Technically, the vulnerability lies within the sapi/apache2handler/sapi_apache2.c file in vulnerable versions of PHP. Attack vectors utilize specially crafted chunked requests to introduce malicious scripts into the server's response. In a typical exploit scenario, the script is reflected back to the user's browser, bypassing client-side input validation mechanisms. The vulnerability is prominently triggered in environments where transfer-encoding mechanisms are poorly handled, particularly under common configurations. The endpoint exposed by this flaw is accessed via HTTP POST requests with a specific payload structure. Given its nature, this vulnerability requires minimal technical expertise to exploit, increasing the risk profile for affected systems.

Exploitation of this XSS vulnerability can lead to significant adverse effects on server and client security. Potential outcomes include theft of session tokens, unauthorized actions impersonating legitimate users, and exfiltration of sensitive data. Attackers might leverage this vulnerability to further compromise server integrity or launch broader attacks against internal network resources. Clients interacting with affected servers risk unwanted exposure to harmful scripts and potential malware distribution. The aggregated consequences of such exploitations underscore the need for immediate remediation actions and heightened focus on input sanitization practices. Ultimately, the reputational damage to affected organizations can translate into severe business impacts.

REFERENCES

• https://bugs.php.net/bug.php?id=76582
• https://github.com/php/php-src/commit/23b057742e3cf199612fa8050ae86cae675e214e
• https://nvd.nist.gov/vuln/detail/CVE-2018-17082
• https://security.gentoo.org/glsa/201812-01
• https://github.com/ockeghem/web-sec-study/blob/master/why-CVE-2018-17082-is-not-XSS/README.md