How severe is CVE-2021-36564?

CVE-2021-36564 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-36564 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-36564?

CVE-2021-36564 affects Thinkphp. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-36564?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-36564 published?

CVE-2021-36564 was published on 2021-12-06 and last updated on 2026-06-17.

CVE-2021-36564

CVE-2021-36564 is a critical-severity vulnerability in Thinkphp with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Thinkphp
Published: 2021-12-06
Last modified: 2026-06-17

Description

ThinkPHP v6.0.8 was discovered to contain a deserialization vulnerability via the component vendor\league\flysystem-cached-adapter\src\Storage\Adapter.php.

Frequently asked questions

What is CVE-2021-36564?: ThinkPHP v6.0.8 was discovered to contain a deserialization vulnerability via the component vendor\league\flysystem-cached-adapter\src\Storage\Adapter.php.
How severe is CVE-2021-36564?: CVE-2021-36564 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-36564 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-36564?: CVE-2021-36564 affects Thinkphp. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-36564?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-36564 published?: CVE-2021-36564 was published on 2021-12-06 and last updated on 2026-06-17.

References

https://github.com/top-think/framework/issues/2559

Affected products (1)

cpe:2.3:a:thinkphp:thinkphp:6.0.8:*:*:*:*:*:*:*

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