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CVE-2021-21705 : What You Need to Know

Discover the impact of CVE-2021-21705 affecting PHP versions 7.3.x, 7.4.x, and 8.0.x. Learn about the URL validation vulnerability, its implications, and mitigation steps.

PHP versions 7.3.x below 7.3.29, 7.4.x below 7.4.21, and 8.0.x below 8.0.8 are affected by a vulnerability in URL validation. When using the filter_var() function with FILTER_VALIDATE_URL parameter, an invalid password field in the URL can be accepted as valid, potentially leading to security implications.

Understanding CVE-2021-21705

This CVE impacts PHP versions 7.3.x, 7.4.x, and 8.0.x by allowing invalid password fields in URLs to be interpreted as valid.

What is CVE-2021-21705?

In PHP versions 7.3.x below 7.3.29, 7.4.x below 7.4.21, and 8.0.x below 8.0.8, an issue with URL validation permits acceptance of URLs with invalid password fields, opening doors to security risks.

The Impact of CVE-2021-21705

The vulnerability can result in PHP incorrectly parsing URLs, potentially leading to serious security implications, such as establishing connections with incorrect servers or making inaccurate access decisions.

Technical Details of CVE-2021-21705

The vulnerability in PHP allows for the acceptance of URLs with invalid password fields, which may lead to various security risks.

Vulnerability Description

The flaw allows URLs with invalid password fields to be considered valid, impacting URL validation functionality within PHP.

Affected Systems and Versions

PHP versions 7.3.x, 7.4.x, and 8.0.x are all affected by this vulnerability in URL validation.

Exploitation Mechanism

By exploiting this vulnerability, attackers could trick the code into parsing URLs incorrectly, potentially compromising system security.

Mitigation and Prevention

Addressing CVE-2021-21705 requires immediate actions along with long-term security practices and timely patching.

Immediate Steps to Take

Developers and administrators should update PHP to versions 7.3.29, 7.4.21, or 8.0.8 to mitigate the risk associated with this vulnerability.

Long-Term Security Practices

Regular security assessments, code reviews, and input validation best practices can help prevent similar vulnerabilities in the future.

Patching and Updates

Stay informed about security advisories from PHP Group and promptly apply patches to ensure systems are protected from known vulnerabilities.

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