CVE-2026-45264Network attack vector

Unauthorized file renames via incomplete ACL check

Published Jun 1, 2026 · Updated Jun 1, 2026

Improper access control in Nextcloud Team Folders allows remote authenticated users to rename files without UPDATE permission. The Team Folders ACL rule check authorizes a rename when the user has READ and CREATE rights, without also enforcing the required UPDATE right. Exploitation requires an account with READ and CREATE access to an ACL-protected team folder; the demonstrated consequence is limited to renaming files in that folder.

CVSS severity4.3
Medium
EPSS probability0.23%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Nextcloud Team Folders allows remote authenticated users to rename files without UPDATE permission. The Team Folders ACL rule check authorizes a rename when the user has READ and CREATE rights, without also enforcing the required UPDATE right. Exploitation requires an account with READ and CREATE access to an ACL-protected team folder; the demonstrated consequence is limited to renaming files in that folder.

The record

CVE
CVE-2026-45264
Published
Jun 1, 2026
Updated
Jun 1, 2026
Vendor
Nextcloud GmbH
Product
Nextcloud Security Advisories
Classifications
CWE-284, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 1, 2026CVE publishedPublication date reported by the CVE source.
  2. 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.

  1. Affected versionversion=>= 17.0.0, < 17.0.15
  2. Affected versionversion=>= 18.0.0, < 18.1.12
  3. Affected versionversion=>= 19.0.0, < 19.1.16
  4. Affected versionversion=>= 20.0.0, < 20.1.11
  5. Affected versionversion=>= 21.0.0, < 21.0.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Security Advisoriesversion=>= 17.0.0, < 17.0.15; version=>= 18.0.0, < 18.1.12; version=>= 19.0.0, < 19.1.16; version=>= 20.0.0, < 20.1.11; version=>= 21.0.0, < 21.0.4

Published CVSS scores

4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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