CVE-2026-45159: CWE-639: Authorization Bypass Through User-Controlled Key in nextcloud security-advisories
Nextcloud is an open source content collaboration platform. From versions 1.15.0 to before 1.15.4, 1.16.0 to before 1.16.3, 1.17.0 to before 1.17.1, and 1.18.0 to before 1.18.1, a malicious user with access to an end-to-end encrypted files drop link was able to also drop files into other end-to-end encrypted folders of the share owner. Reading and modifying of other files was not possible. This issue has been patched in versions 1.15.4, 1.16.3, 1.17.1, 1.18.1, and 2.0.0-rc.7.
AI Analysis
Technical Summary
CVE-2026-45159 is an authorization bypass vulnerability in Nextcloud's end-to-end encrypted file sharing feature. Specifically, in affected versions, a malicious user with access to a drop link could place files into other encrypted folders of the share owner without permission. The vulnerability does not permit reading or modifying existing files, only unauthorized file dropping. The flaw is classified under CWE-639 (Authorization Bypass Through User-Controlled Key). Official patches have been released in Nextcloud versions 1.15.4, 1.16.3, 1.17.1, 1.18.1, and 2.0.0-rc.7 to address this issue.
Potential Impact
The impact is limited to unauthorized file addition into end-to-end encrypted folders of the share owner. There is no confidentiality breach as reading files is not possible, nor is modification of existing files. The integrity impact is low since only file dropping is possible, which could potentially be used to introduce unwanted files but not alter or read existing content.
Mitigation Recommendations
A fix is available and has been released in Nextcloud versions 1.15.4, 1.16.3, 1.17.1, 1.18.1, and 2.0.0-rc.7. Users of affected versions should upgrade to one of these patched versions to remediate the vulnerability. Patch status is confirmed by the vendor advisory. No additional mitigation steps are indicated.
CVE-2026-45159: CWE-639: Authorization Bypass Through User-Controlled Key in nextcloud security-advisories
Description
Nextcloud is an open source content collaboration platform. From versions 1.15.0 to before 1.15.4, 1.16.0 to before 1.16.3, 1.17.0 to before 1.17.1, and 1.18.0 to before 1.18.1, a malicious user with access to an end-to-end encrypted files drop link was able to also drop files into other end-to-end encrypted folders of the share owner. Reading and modifying of other files was not possible. This issue has been patched in versions 1.15.4, 1.16.3, 1.17.1, 1.18.1, and 2.0.0-rc.7.
CVSS v3.1
Score 3.5low
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-45159 is an authorization bypass vulnerability in Nextcloud's end-to-end encrypted file sharing feature. Specifically, in affected versions, a malicious user with access to a drop link could place files into other encrypted folders of the share owner without permission. The vulnerability does not permit reading or modifying existing files, only unauthorized file dropping. The flaw is classified under CWE-639 (Authorization Bypass Through User-Controlled Key). Official patches have been released in Nextcloud versions 1.15.4, 1.16.3, 1.17.1, 1.18.1, and 2.0.0-rc.7 to address this issue.
Potential Impact
The impact is limited to unauthorized file addition into end-to-end encrypted folders of the share owner. There is no confidentiality breach as reading files is not possible, nor is modification of existing files. The integrity impact is low since only file dropping is possible, which could potentially be used to introduce unwanted files but not alter or read existing content.
Mitigation Recommendations
A fix is available and has been released in Nextcloud versions 1.15.4, 1.16.3, 1.17.1, 1.18.1, and 2.0.0-rc.7. Users of affected versions should upgrade to one of these patched versions to remediate the vulnerability. Patch status is confirmed by the vendor advisory. No additional mitigation steps are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-05-08T20:44:38.965Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a1dbba7e29bf47b501c5800
Added to database: 6/1/2026, 5:04:39 PM
Last enriched: 6/1/2026, 5:20:23 PM
Last updated: 6/2/2026, 6:21:31 AM
Views: 17
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