Use After Free in Php
CVE-2021-21708
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.
Vulnerability class: Use-After-Free
EPSS: 0.030 (86.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L.
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security@php.net (Exploit, Patch, x_refsource_MISC, Issue Tracking, Vendor Advisory)
- security@php.net (x_refsource_CONFIRM, Third Party Advisory)
- security@php.net (vendor-advisory, Third Party Advisory, x_refsource_GENTOO)
Frequently asked questions
- What is CVE-2021-21708?
- CVE-2021-21708 is a high-severity vulnerability in Php, classified under Use After Free. CVSS score: 8.2/10. Published 2022-02-27.
- How severe is CVE-2021-21708?
- High severity. CVSS v3 base score is 8.2 out of 10.
- Is CVE-2021-21708 known to be exploited?
- 3 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.