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Vulnerability record · CVE-2021-21705 · published 4 October 2021

CVE-2021-21705: Php improper input validation vulnerability

Php · Php

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, when using URL validation functionality via filter_var() function with FILTER_VALIDATE_URL parameter, an URL with invalid password field can be accepted as valid. This can lead to the code incorrectly parsing the URL and potentially leading to other security implications - like contacting a wrong server or making a wrong access decision.

5.3 CVSS 3.1 Medium EPSS 2.1% · top 19.1% CWE-20 · Improper input validation
5.3CVSS 3.1 base score, v2 5.0
2.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

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, when using URL validation functionality via filter_var() function with FILTER_VALIDATE_URL parameter, an URL with invalid password field can be accepted as valid. This can lead to the code incorrectly parsing the URL and potentially leading to other security implications - like contacting a wrong server or making a wrong access decision.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.php.net/bug.php?id=81122 ExploitIssue TrackingPatchVendor Advisory
https://security.gentoo.org/glsa/202209-20 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211029-0006/ Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchVendor Advisory
https://bugs.php.net/bug.php?id=81122 ExploitIssue TrackingPatchVendor Advisory
https://security.gentoo.org/glsa/202209-20 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211029-0006/ Third Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchVendor Advisory

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-21705), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.