Existence of calendars and address books can be checked by unauthenticated users
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- Low · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-284.
Summary
Nextcloud Server provides data storage for Nextcloud, an open source cloud platform. Starting in version 25.0.0 and prior to versions 25.0.9, 26.0.4, and 27.0.1, unauthenticated users could send a DAV request which reveals whether a calendar or an address book with the given identifier exists for the victim. Nextcloud Server versions 25.0.9, 26.0.4, and 27.0.1 and Nextcloud Enterprise Server versions 25.0.9, 26.0.4, and 27.0.1 contain a patch for this issue. No known workarounds are available.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| nextcloud | security-advisories | 25.0.0 to before 25.0.9; 26.0.0 to before 26.0.4; 27.0.0 to before 27.0.1 | 25.0.9, 26.0.4, 27.0.1 | Patch available | CNA |
- security-advisories Vendornextcloud Affected 25.0.0 to before 25.0.9; 26.0.0 to before 26.0.4; 27.0.0 to before 27.0.1 Fixed in 25.0.9, 26.0.4, 27.0.1 Patch available CNA
CPE configurations NVD · 6
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:* | 25.0.0 to before 25.0.9 | Vulnerable | nextcloud |
| cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:* | 25.0.0 to before 25.0.9 | Vulnerable | nextcloud |
| cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:* | 26.0.0 to before 26.0.4 | Vulnerable | nextcloud |
| cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:* | 26.0.0 to before 26.0.4 | Vulnerable | nextcloud |
| cpe:2.3:a:nextcloud:nextcloud_server:27.0.0:*:*:*:-:*:*:* | 27.0.0 | Vulnerable | nextcloud |
| cpe:2.3:a:nextcloud:nextcloud_server:27.0.0:*:*:*:enterprise:*:*:* | 27.0.0 | Vulnerable | nextcloud |
- cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:* Versions 25.0.0 to before 25.0.9 Vulnerable ·nextcloud
- cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:* Versions 25.0.0 to before 25.0.9 Vulnerable ·nextcloud
- cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:-:*:*:* Versions 26.0.0 to before 26.0.4 Vulnerable ·nextcloud
- cpe:2.3:a:nextcloud:nextcloud_server:*:*:*:*:enterprise:*:*:* Versions 26.0.0 to before 26.0.4 Vulnerable ·nextcloud
- cpe:2.3:a:nextcloud:nextcloud_server:27.0.0:*:*:*:-:*:*:* Versions 27.0.0 Vulnerable ·nextcloud
- cpe:2.3:a:nextcloud:nextcloud_server:27.0.0:*:*:*:enterprise:*:*:* Versions 27.0.0 Vulnerable ·nextcloud
Remediation
- Fix · CNA security-advisories (nextcloud) Fixed in 25.0.9, 26.0.4, 27.0.1
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2023-39959
References
More Nextcloud Server vulnerabilities
- 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
Sources
- CVE-2023-39959 · CVE Program
- CVE-2023-39959 · NVD
- FIRST EPSS
- CVE-2023-39959 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences