How severe is CVE-2021-37630?

CVE-2021-37630 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-2021-37630 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-37630?

CVE-2021-37630 affects Nextcloud Circles. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-37630?

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

When was CVE-2021-37630 published?

CVE-2021-37630 was published on 2021-09-07 and last updated on 2026-06-17.

CVE-2021-37630

CVE-2021-37630 is a medium-severity vulnerability in Nextcloud Circles 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-639.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.0
EPSS exploit prediction: 1% (67th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-639
Affected product: Nextcloud Circles
Published: 2021-09-07
Last modified: 2026-06-17

Description

Nextcloud Circles is an open source social network built for the nextcloud ecosystem. In affected versions the Nextcloud Circles application allowed any user to join any "Secret Circle" without approval by the Circle owner leaking private information. It is recommended that Nextcloud Circles is upgraded to 0.19.15, 0.20.11 or 0.21.4. There are no workarounds for this issue.

Frequently asked questions

What is CVE-2021-37630?: Nextcloud Circles is an open source social network built for the nextcloud ecosystem. In affected versions the Nextcloud Circles application allowed any user to join any "Secret Circle" without approval by the Circle owner leaking private information. It is recommended that Nextcloud Circles is upgraded to 0.19.15, 0.20.11 or 0.21.4. There are no workarounds for this issue.
How severe is CVE-2021-37630?: CVE-2021-37630 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-2021-37630 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (67th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-37630?: CVE-2021-37630 affects Nextcloud Circles. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-37630?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-37630 published?: CVE-2021-37630 was published on 2021-09-07 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nextcloud:circles:*:*:*:*:*:*:*:*

More vulnerabilities in Nextcloud Circles

CVE-2021-32782 — Medium (CVSS 5.8): Nextcloud Circles is an open source social network built for the nextcloud ecosystem. In affected versions the…
CVE-2019-15610 — Medium (CVSS 4.3): Improper authorization in the Circles app 0.17.7 causes retaining access when an email address was removed from a…

All CVEs affecting Nextcloud Circles →

Other CWE-639 (Authorization Bypass Through User-Controlled Key (IDOR)) vulnerabilities

CVE-2026-69865 — Critical (CVSS 10.0): Authorization bypass through user-controlled key in Microsoft Container Registry allows an unauthorized attacker to…
CVE-2026-83711 — Critical (CVSS 10.0): Authorization bypass through user-controlled key in Microsoft Azure Active Directory B2C allows an unauthorized…
CVE-2026-77998 — Critical (CVSS 10.0): Joomla Extension - miniorange.com - Unauthenticated Authentication Bypass via SAMLResponse Parameter in miniOrange SAML…
CVE-2026-77995 — Critical (CVSS 10.0): Joomla Extension - miniorange.com - Arbitrary account takeover in miniOrange OAuth Client < 3.2.0, OAuth Single Sign-On…
CVE-2025-40805 — Critical (CVSS 10.0): Affected devices do not properly enforce user authentication on specific API endpoints. This could facilitate an…
CVE-2024-45032 — Critical (CVSS 10.0): A vulnerability has been identified in Industrial Edge Management Pro (All versions < V1.9.5), Industrial Edge…

Browse all CWE-639 (Authorization Bypass Through User-Controlled Key (IDOR)) vulnerabilities →