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
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.030 (86.9th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 87th percentile — 86.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.030 · newest: 0.030 · change: 0.000
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- bugs.php.net/bug.php (Exploit, Patch, Issue Tracking, Vendor Advisory)
- security.netapp.com/advisory/ntap-20220325-0004/ (Third Party Advisory)
- security.gentoo.org/glsa/202209-20 (vendor-advisory, Third Party Advisory)
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.