CVE-2025-59788
📋 TL;DR
This CVE describes a cross-site scripting (XSS) vulnerability in Nextcloud's files_pdfviewer example directory. Attackers can execute arbitrary JavaScript in users' browsers by uploading a crafted PDF file to viewer.html. This affects Nextcloud instances with exposed example code on same-origin basis across multiple versions.
💻 Affected Systems
- Nextcloud
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Attackers could steal session cookies, perform actions as authenticated users, redirect to malicious sites, or install malware via drive-by downloads.
Likely Case
Session hijacking, credential theft, or unauthorized actions within the Nextcloud instance.
If Mitigated
Limited impact if proper input validation and output encoding are implemented, or if example directories are removed.
🎯 Exploit Status
Exploitation requires uploading a crafted PDF file to the vulnerable viewer.html endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 22.2.10.33, 23.0.12.29, 24.0.12.28, 25.0.13.23, 26.0.13.20, 27.1.11.20, 28.0.14.11, 29.0.16.8, 30.0.17, 31.0.10, 32.0.1 or later
Vendor Advisory: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-24wp-p865-7j4r
Restart Required: No
Instructions:
1. Update Nextcloud to the patched version. 2. Follow Nextcloud's standard update procedure. 3. Verify the update completed successfully.
🔧 Temporary Workarounds
Remove example directory
linuxDelete or restrict access to the files_pdfviewer example directory
rm -rf /path/to/nextcloud/apps/files_pdfviewer/example/
Restrict file uploads
allImplement strict file upload validation for PDF files
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block malicious PDF uploads
- Disable or restrict access to the files_pdfviewer app entirely
🔍 How to Verify
Check if Vulnerable:
Check if Nextcloud version is in affected range and if files_pdfviewer/example/viewer.html is accessibleCheck Version:
php occ status | grep 'versionstring'Verify Fix Applied:
Verify Nextcloud version is patched and test that crafted PDF files no longer execute JavaScript📡 Detection & Monitoring
Log Indicators:
- Unusual PDF file uploads
- Access to files_pdfviewer/example/viewer.html
- JavaScript execution errors in logs
Network Indicators:
- HTTP requests to viewer.html with PDF parameters
- Unusual outbound connections after PDF upload
SIEM Query:
source="nextcloud.log" AND ("viewer.html" OR "files_pdfviewer/example")