Quick answers
- Is CVE-2026-35031 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-35031 being exploited in the wild.
- How severe is CVE-2026-35031?
- Critical severity, with a CVSS score of 9.9, published 14 April 2026.
- Which products and versions are affected?
- Jellyfin < 10.11.7.
- Is there a fix for CVE-2026-35031?
- A patch was published on 2026-03-31: Version 10.11.7 released with security fixes. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-35031 attacked?
- It is attacked over the network, in a network appliance.
- Am I affected by CVE-2026-35031?
- Check whether you run Jellyfin at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
Technical details
A vulnerability chain exists in the Jellyfin subtitle upload endpoint (POST /Videos/{itemId}/Subtitles) due to improper validation of the 'Format' field. An attacker can use path traversal sequences in the file extension to perform an arbitrary file write. This can be further chained by writing malicious .strm files to achieve arbitrary file read, extracting the database to escalate privileges to administrator, and finally achieving remote code execution (RCE) as root by overwriting /etc/ld.so.preload. Exploitation requires 'Subtitle Management' permissions, which are held by administrators or users specifically granted upload rights. The issue is resolved in version 10.11.7 through improved input sanitization.
Affected products
- Jellyfin Jellyfin < 10.11.7
Timeline
- 2026-03-31: patched: Version 10.11.7 released with security fixes.
- 2026-04-14: disclosed: Security advisory published.
- 2026-04-14: advisory