How severe is CVE-2021-20866?

CVE-2021-20866 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2021-20866 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20866?

CVE-2021-20866 primarily affects Advancedcustomfields Advanced Custom Fields. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20866?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-20866 published?

CVE-2021-20866 was published on 2021-12-13 and last updated on 2026-06-17.

CVE-2021-20866

CVE-2021-20866 is a medium-severity vulnerability in Advancedcustomfields Advanced Custom Fields with a CVSS 3.x base score of 6.5. 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-862.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.0
EPSS exploit prediction: 2% (74th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Advancedcustomfields Advanced Custom Fields
Published: 2021-12-13
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-20866?: 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.
How severe is CVE-2021-20866?: CVE-2021-20866 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2021-20866 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20866?: CVE-2021-20866 primarily affects Advancedcustomfields Advanced Custom Fields. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20866?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20866 published?: CVE-2021-20866 was published on 2021-12-13 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:advancedcustomfields:advanced_custom_fields:*:*:*:*:*:wordpress:*:*
cpe:2.3:a:advancedcustomfields:advanced_custom_fields:*:*:*:*:pro:wordpress:*:*

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