Vulnerability Description
Jellyfin is an open source self hosted media server. Versions prior to 10.11.7 contain a vulnerability chain in the subtitle upload endpoint (POST /Videos/{itemId}/Subtitles), where the Format field is not validated, allowing path traversal via the file extension and enabling arbitrary file write. This arbitrary file write can be chained into arbitrary file read via .strm files, database extraction, admin privilege escalation, and ultimately remote code execution as root via ld.so.preload. Exploitation requires an administrator account or a user that has been explicitly granted the "Upload Subtitles" permission. This issue has been fixed in version 10.11.7. If users are unable to upgrade immediately, they can grant non-administrator users Subtitle upload permissions to reduce attack surface.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Jellyfin | Jellyfin | < 10.11.7 |
Related Weaknesses (CWE)
References
- https://github.com/jellyfin/jellyfin/releases/tag/v10.11.7ProductRelease Notes
- https://github.com/jellyfin/jellyfin/security/advisories/GHSA-j2hf-x4q5-47j3MitigationVendor Advisory
FAQ
What is CVE-2026-35031?
CVE-2026-35031 is a vulnerability with a CVSS score of 9.9 (CRITICAL). Jellyfin is an open source self hosted media server. Versions prior to 10.11.7 contain a vulnerability chain in the subtitle upload endpoint (POST /Videos/{itemId}/Subtitles), where the Format field i...
How severe is CVE-2026-35031?
CVE-2026-35031 has been rated CRITICAL with a CVSS base score of 9.9/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-35031?
Check the references section above for vendor advisories and patch information. Affected products include: Jellyfin Jellyfin.