🛡️ CVE-2021-21708 on Debian — php7.4

⚪ Unknown ✅ No Known Exploit OSV

N/A

CVSS Score

0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2021-21708 as tracked by Debian, for the package php7.4. The fix is available in version 7.4.28-1+deb11u1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Affected software

DEBIAN-CVE-2021-21708 is recorded against 1 package.

php7.4 (fixed in 7.4.28-1+deb11u1)

Timeline and source

Published on 27 February 2022 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2021-21708 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Base record Ubuntu

Details

Severity Unknown

CVSS Score N/A

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

CWE N/A

Public Exploit ✅ No

Source OSV

Published 2022-02-27

Updated 2026-08-11

Modified 2026-08-04

Fix URL N/A

Affected Packages

Software	From version	Fixed in
php7.4	—	7.4.28-1+deb11u1

References

ADVISORY https://security-tracker.debian.org/tracker/CVE-2021-21708

🔗 NVD 🔗 Mitre

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