Nextcloud Calendar up to 5.5.16/6.2.2 information disclosure

Summaryinfo

A vulnerability has been found in Nextcloud Calendar up to 5.5.16/6.2.2 and classified as problematic. Affected by this vulnerability is an unknown functionality. This manipulation causes information disclosure. This vulnerability is handled as CVE-2026-45286. The attack can be initiated remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as problematic was found in Nextcloud Calendar up to 5.5.16/6.2.2. Affected by this vulnerability is an unknown part. The manipulation with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. The summary by CVE is:

Nextcloud is an open source content collaboration platform. From versions 5.5.13 to before 5.5.17, and 6.2.0 to before 6.2.3, an authenticated user can enumerate users on the same Nextcloud instance by using the Calendar app's endpoint for suggesting attendees. The sharing restrictions, applied to other endpoints, were not effective here. This issue has been patched in versions 5.5.17 and 6.2.3.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-45286 since 05/11/2026. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1592 for this issue.

Upgrading to version 5.5.17 or 6.2.3 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Type

• Calendar Software

Vendor

• Nextcloud

Name

• Calendar

Version

• 5.5.0
• 5.5.1
• 5.5.2
• 5.5.3
• 5.5.4
• 5.5.5
• 5.5.6
• 5.5.7
• 5.5.8
• 5.5.9
• 5.5.10
• 5.5.11
• 5.5.12
• 5.5.13
• 5.5.14
• 5.5.15
• 5.5.16
• 6.2.0
• 6.2.1
• 6.2.2

License

• open-source

Website

• Product: https://github.com/nextcloud/calendar/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Discussion