Read the docs
TI-2026-33081 Aliases CVE-2026-45281

Nextcloud: Cross-Account Calendar Takeover via Unauthorized Group-Member-Set Update

Priority LOW 37CWE-639Published · Updated

Key facts

Attack vector
Network
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-639.

Summary

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, with the knowledge of other users’ principal URL an attacker could possibly send a request to gain full access to their calendar. Therefore, the attacker must be an authenticated user. This is because of improper authorization controls in the backend of the calendar. If the attacker had access to the calendar, they would be able to view and modify it. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00284 21st percentileScored 2026-11-07
Fix Fixed security-advisories (nextcloud): 32.0.9, 33.0.3

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
nextcloudsecurity-advisories32.0.0 to before 32.0.9; 33.0.0 to before 33.0.332.0.9, 33.0.3Patch availableCNA
  • security-advisories Vendornextcloud Affected 32.0.0 to before 32.0.9; 33.0.0 to before 33.0.3 Fixed in 32.0.9, 33.0.3 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:*32.0.0 to before 32.0.9; 33.0.0 to before 33.0.3Vulnerablenextcloud
cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:*21.0.0 to before 21.0.9.23; 22.0.0 to before 22.2.10.39; 23.0.0 to before 23.0.12.35; 24.0.0 to before 24.0.12.34; 25.0.0 to before 25.0.13.29; 26.0.0 to before 26.0.13.26; 27.0.0 to before 27.1.11.26; 28.0.0 to before 28.0.14.17; 29.0.0 to before 29.0.16.16; 30.0.0 to before 30.0.17.9; 31.0.0 to before 31.0.14.5; 32.0.0 to before 32.0.9; 33.0.0 to before 33.0.3Vulnerablenextcloud
  • cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:* Versions 32.0.0 to before 32.0.9; 33.0.0 to before 33.0.3 Vulnerable ·nextcloud
  • cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:* Versions 21.0.0 to before 21.0.9.23; 22.0.0 to before 22.2.10.39; 23.0.0 to before 23.0.12.35; 24.0.0 to before 24.0.12.34; 25.0.0 to before 25.0.13.29; 26.0.0 to before 26.0.13.26; 27.0.0 to before 27.1.11.26; 28.0.0 to before 28.0.14.17; 29.0.0 to before 29.0.16.16; 30.0.0 to before 30.0.17.9; 31.0.0 to before 31.0.14.5; 32.0.0 to before 32.0.9; 33.0.0 to before 33.0.3 Vulnerable ·nextcloud

Remediation

  • Fix · CNA security-advisories (nextcloud) Fixed in 32.0.9, 33.0.3

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-45281

References

Patch 1

Advisory 1

Other 1

  • TI-2023-20855 Users can delete external storage mount points CVSS 3.1HIGH 7.7
  • TI-2023-11091 Nextcloud download permissions can be changed by resharer CVSS 3.1HIGH 7.5
  • TI-2023-10624 Nextcloud Server vulnerable to SSRF via filter bypass due to lax checking on IPs CVSS 3.1MEDIUM 5.3
  • TI-2025-37238 Cross-site scripting in Nextcloud CVSS 3.1MEDIUM 6.4
  • TI-2023-11086 nextcloud vulnerable to Uncontrolled Resource Consumption CVSS 3.1MEDIUM 6.5
  • TI-2022-18738 Exception logging in Sharepoint app reveals clear-text connection details CVSS 3.1MEDIUM 6.5
See all 188 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences