CVE-2021-21707 : Vulnerability Insights and Analysis

A vulnerability in certain XML parsing functions in PHP versions 7.3.x, 7.4.x, and 8.0.x could allow an attacker to manipulate filenames, potentially leading to reading unintended files.

Understanding CVE-2021-21707

This CVE identifies a security issue in PHP versions that could be exploited through XML parsing functions.

What is CVE-2021-21707?

In PHP versions 7.3.x below 7.3.33, 7.4.x below 7.4.26, and 8.0.x below 8.0.13, certain XML parsing functions may misinterpret filenames with URL-encoded NUL characters, potentially resulting in reading unintended files.

The Impact of CVE-2021-21707

Exploitation of this vulnerability could allow a malicious actor to manipulate filenames and trick the system into parsing a different file than intended, potentially exposing sensitive data.

Technical Details of CVE-2021-21707

This section elaborates on the specifics of the vulnerability.

Vulnerability Description

The vulnerability arises from the URL decoding process within specific XML parsing functions, leading to a misinterpretation of filenames.

Affected Systems and Versions

Vendor: PHP Group
Product: PHP
Affected Versions: 7.3.x < 7.3.33, 7.4.x < 7.4.26, 8.0.x < 8.0.13

Exploitation Mechanism

Attackers may exploit this issue by crafting filenames containing URL-encoded NUL characters to manipulate file parsing.

Mitigation and Prevention

Protective measures to address and prevent exploitation of this vulnerability.

Immediate Steps to Take

Users should update their PHP installations to versions 7.3.33, 7.4.26, or 8.0.13 to mitigate the risk associated with this vulnerability.

Long-Term Security Practices

Ensure regular security updates and monitoring to mitigate potential risks associated with similar vulnerabilities in the future.

Patching and Updates

Stay informed about security advisories and apply patches promptly to maintain a secure PHP environment.