CVE-2021-21708

Name: CVE-2021-21708
Creator: NVD / NIST
Published: 2022-02-27T08:15:06.817+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 3.00%

Last modified Jun 17, 2026

CVE-2021-21708 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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.. EPSS estimates a 3.00% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

3.00%

85.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Php	Php	>= 7.4.0, < 7.4.28
Php	Php	>= 8.0.0, < 8.0.16
Php	Php	>= 8.1.0, < 8.1.3

References

https://bugs.php.net/bug.php?id=81708Exploit, Issue Tracking, Patch, Vendor Advisory
https://security.gentoo.org/glsa/202209-20Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0004/Third Party Advisory
https://bugs.php.net/bug.php?id=81708Exploit, Issue Tracking, Patch, Vendor Advisory
https://security.gentoo.org/glsa/202209-20Third Party Advisory
https://security.netapp.com/advisory/ntap-20220325-0004/Third Party Advisory

Timeline

Published: Feb 27, 2022
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21708?

How severe is CVE-2021-21708?

CVE-2021-21708 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 3.00% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21708?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21708?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST