What is CVE-2021-36567?

CVE-2021-36567 is a critical-severity vulnerability in Thinkphp, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-12-06.

How severe is CVE-2021-36567?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Is CVE-2021-36567 known to be exploited?

2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Deserialization in Thinkphp

CVE-2021-36567

ThinkPHP v6.0.8 was discovered to contain a deserialization vulnerability via the component League\Flysystem\Cached\Storage\AbstractCache.

Vulnerability class: Insecure Deserialization

Published 2021-12-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.025 (84.0th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 84.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.024 · newest: 0.025 · change: +0.001

Affected products

Thinkphp — versions 6.0.8

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

Public proof-of-concept exploits

References

github.com/top-think/framework/issues/2561 (Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2021-36567?: CVE-2021-36567 is a critical-severity vulnerability in Thinkphp, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2021-12-06.
How severe is CVE-2021-36567?: Critical severity. CVSS v3 base score is 9.8 out of 10.
Is CVE-2021-36567 known to be exploited?: 2 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.