Vulnerability record · CVE-2021-21708 · published 27 February 2022

CVE-2021-21708: Php use after free vulnerability

Php · Php

In PHP versions 7.4.x below 7.4.28, 8.0.x below 8.0.16, and 8.1.x below 8.1.3, when using filter functions with FILTER_VALIDATE_FLOAT filter and min/max limits, if the filter fails, there is a possibility to trigger use of allocated memory after free, which can result it crashes, and potentially in overwrite of other memory chunks and RCE. This issue affects: code that uses FILTER_VALIDATE_FLOAT with min/max limits.

9.8 CVSS 3.1 Critical EPSS 3.0% · top 13.1% CWE-416 · Use after free

9.8CVSS 3.1 base score, v2 6.8

3.0%EPSS exploitation probability, 30 days

NoNot in CISA KEV

1Affected product versions listed by NVD

6References, 2 tagged exploit

17 Jun 2026Last modified by NVD

Description

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

Affected products

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

Php Php

References

Link	Tags
https://bugs.php.net/bug.php?id=81708	ExploitIssue TrackingPatchVendor Advisory
https://security.gentoo.org/glsa/202209-20	Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0004/	Third Party Advisory
https://bugs.php.net/bug.php?id=81708	ExploitIssue TrackingPatchVendor Advisory
https://security.gentoo.org/glsa/202209-20	Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0004/	Third Party 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-2021-21708), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.