CVE-2021-20866

Name: CVE-2021-20866
Creator: NVD / NIST
Published: 2021-12-13T07:15:06.937+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.5/10EPSS 1.66%

Last modified Jun 17, 2026

CVE-2021-20866 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. Advanced Custom Fields versions prior to 5.11 and Advanced Custom Fields Pro versions prior to 5.11 contain a missing authorization vulnerability in obtaining the user list which may allow a user to obtain the unauthorized information via unspecified vectors.. EPSS estimates a 1.66% chance of exploitation in the next 30 days.

Description

Advanced Custom Fields versions prior to 5.11 and Advanced Custom Fields Pro versions prior to 5.11 contain a missing authorization vulnerability in obtaining the user list which may allow a user to obtain the unauthorized information via unspecified vectors.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

1.66%

73.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-862

Affected Software

Vendor	Product	Versions
Advancedcustomfields	Advanced Custom Fields	< 5.11

References

https://jvn.jp/en/jp/JVN09136401/index.htmlThird Party Advisory
https://wordpress.org/plugins/advanced-custom-fields/Third Party Advisory
https://www.advancedcustomfields.com/Vendor Advisory
https://jvn.jp/en/jp/JVN09136401/index.htmlThird Party Advisory
https://wordpress.org/plugins/advanced-custom-fields/Third Party Advisory
https://www.advancedcustomfields.com/Vendor Advisory

Timeline

Published: Dec 13, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20866?

How severe is CVE-2021-20866?

CVE-2021-20866 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 1.66% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20866?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20866?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST