Authenticated user enumeration via unrestricted attendee suggestions
Published Jun 1, 2026 · Updated Jun 1, 2026
Information disclosure in Nextcloud Calendar 5.5.13 through 5.5.16 and 6.2.0 through 6.2.2 allows remote authenticated users to enumerate accounts. The searchAttendee endpoint called the contacts manager with enumeration enabled and omitted the core sharing and group-restriction checks used elsewhere. Any authenticated instance user could submit partial attendee text and receive matching user names and email addresses across otherwise separated groups.
Summary
What happened
Information disclosure in Nextcloud Calendar 5.5.13 through 5.5.16 and 6.2.0 through 6.2.2 allows remote authenticated users to enumerate accounts. The searchAttendee endpoint called the contacts manager with enumeration enabled and omitted the core sharing and group-restriction checks used elsewhere. Any authenticated instance user could submit partial attendee text and receive matching user names and email addresses across otherwise separated groups.
The record
- CVE
- CVE-2026-45286
- Published
- Jun 1, 2026
- Updated
- Jun 1, 2026
- Vendor
- Nextcloud GmbH
- Product
- Security Advisories
- Classifications
- CWE-200, T1087
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Jun 1, 2026CVE publishedPublication date reported by the CVE source.
- Jun 1, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 5.5.13, < 5.5.17
- Affected versionversion=>= 6.2.0, < 6.2.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Attendee autocomplete reproduction stepsproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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