How severe is CVE-2021-41239?

CVE-2021-41239 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2021-41239 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-41239?

CVE-2021-41239 primarily affects Nextcloud Nextcloud Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-41239?

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

When was CVE-2021-41239 published?

CVE-2021-41239 was published on 2022-03-08 and last updated on 2026-06-17.

CVE-2021-41239

CVE-2021-41239 is a medium-severity vulnerability in Nextcloud Nextcloud Server with a CVSS 3.x base score of 5.3. 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 5.3)
CVSS v2: 5.0
EPSS exploit prediction: 1% (62nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-862
Affected product: Nextcloud Nextcloud Server
Published: 2022-03-08
Last modified: 2026-06-17

Description

Nextcloud server is a self hosted system designed to provide cloud style services. In affected versions the User Status API did not consider the user enumeration settings by the administrator. This allowed a user to enumerate other users on the instance, even when user listings where disabled. It is recommended that the Nextcloud Server is upgraded to 20.0.14, 21.0.6 or 22.2.1. There are no known workarounds.

Frequently asked questions

What is CVE-2021-41239?: Nextcloud server is a self hosted system designed to provide cloud style services. In affected versions the User Status API did not consider the user enumeration settings by the administrator. This allowed a user to enumerate other users on the instance, even when user listings where disabled. It is recommended that the Nextcloud Server is upgraded to 20.0.14, 21.0.6 or 22.2.1. There are no known workarounds.
How severe is CVE-2021-41239?: CVE-2021-41239 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2021-41239 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (62nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-41239?: CVE-2021-41239 primarily affects Nextcloud Nextcloud Server. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-41239?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-41239 published?: CVE-2021-41239 was published on 2022-03-08 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:*:*:*:*
cpe:2.3:a:nextcloud:nextcloud_server:22.2.0:*:*:*:*:*:*:*

More vulnerabilities in Nextcloud Nextcloud Server

CVE-2021-22915 — Critical (CVSS 9.8): Nextcloud server before 19.0.11, 20.0.10, 21.0.2 is vulnerable to brute force attacks due to lack of inclusion of IPv6…
CVE-2021-32802 — Critical (CVSS 9.3): Nextcloud server is an open source, self hosted personal cloud. Nextcloud supports rendering image previews for user…
CVE-2023-26482 — Critical (CVSS 9.0): Nextcloud server is an open source home cloud implementation. In affected versions a missing scope validation allowed…
CVE-2021-32688 — High (CVSS 8.8): Nextcloud Server is a Nextcloud package that handles data storage. Nextcloud Server supports application specific…
CVE-2018-3775 — High (CVSS 8.8): Improper Authentication in Nextcloud Server prior to version 12.0.3 would allow an attacker that obtained user…
CVE-2023-35172 — High (CVSS 8.7): NextCloud Server and NextCloud Enterprise Server provide file storage for Nextcloud, a self-hosted productivity…

All CVEs affecting Nextcloud Nextcloud Server →

Other CWE-862 (Missing Authorization) vulnerabilities

CVE-2026-0092 — Critical (CVSS 10.0): In Package Manager, there is a possible device lock controller bypass due to a missing permission check. This could…
CVE-2026-33712 — Critical (CVSS 10.0): Typebot is a chatbot builder tool. In versions 3.15.2 and prior, the preview chat endpoint (POST…
CVE-2026-2031 — Critical (CVSS 10.0): An Improper Access Control vulnerability in several internal API endpoints for Google Cloud Application Integration…
CVE-2026-34976 — Critical (CVSS 10.0): Dgraph is an open source distributed GraphQL database. Prior to 25.3.1, the restoreTenant admin mutation is missing…
CVE-2025-30416 — Critical (CVSS 10.0): Sensitive data disclosure and manipulation due to missing authorization. The following products are affected: Acronis…
CVE-2025-45854 — Critical (CVSS 10.0): /server/executeExec of JEHC-BPM 2.0.1 allows attackers to execute arbitrary code via execParams.

Browse all CWE-862 (Missing Authorization) vulnerabilities →