Is CVE-2026-45286 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-45286 being exploited in the wild.

How severe is CVE-2026-45286?

Medium severity, with a CVSS score of 4.3, published 1 June 2026.

Which products and versions are affected?

Nextcloud Calendar 5.5.13 to < 5.5.17, 6.2.0 to < 6.2.3.

Is there a fix for CVE-2026-45286?

A patch was published on 2026-04-23: Fix merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-45286 attacked?

It is attacked over the network, in a network appliance.

Am I affected by CVE-2026-45286?

Check whether you run Nextcloud Calendar at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-45286: Nextcloud Calendar user enumeration via attendee suggestion endpoint

Q: Is there a fix for CVE-2026-45286?

A patch was published on 2026-04-23: Fix merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-45286 attacked?

It is attacked over the network, in a network appliance.

Q: Am I affected by CVE-2026-45286?

Check whether you run Nextcloud Calendar at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-45286 · Severity: medium · CVSS 4.3 · Published 2026-06-01

Nextcloud is a collaboration platform used for file sharing and team coordination. A flaw in its Calendar application allowed logged-in users to see the names and email addresses of other users on the same system, even when privacy settings were configured to prevent this. This could lead to unauthorized internal data discovery or the exposure of user identities across different departments or client groups.

Technologies: Nextcloud Calendar. Vendors: Nextcloud.

Quick answers

Is CVE-2026-45286 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-45286 being exploited in the wild.
How severe is CVE-2026-45286?: Medium severity, with a CVSS score of 4.3, published 1 June 2026.
Which products and versions are affected?: Nextcloud Calendar 5.5.13 to < 5.5.17, 6.2.0 to < 6.2.3.
Is there a fix for CVE-2026-45286?: A patch was published on 2026-04-23: Fix merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-45286 attacked?: It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-45286?: Check whether you run Nextcloud Calendar at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An information disclosure vulnerability (CWE-200) exists in the Nextcloud Calendar app's attendee suggestion endpoint. While Nextcloud provides administrative settings to restrict user autocompletion and sharing visibility between groups, this specific endpoint failed to respect those global sharing restrictions. An authenticated attacker can send requests to the suggestion endpoint to systematically enumerate user identifiers and email addresses across the entire instance. The issue is resolved in Calendar app versions 5.5.17 and 6.2.3.

Affected products

Nextcloud Calendar app 5.5.13 to < 5.5.17, 6.2.0 to < 6.2.3

Timeline

2026-02-09: disclosed: Initial bug report on GitHub
2026-04-23: patched: Fix merged into main branch
2026-05-12: advisory: Vendor security advisory published
2026-06-01: other: CVE published to NVD

References

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