Path Traversal in Jellyfin

CVE-2026-35031

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.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.9 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.009 (59.8th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 60th percentile — 59.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-35031: held from 0.008 to 0.009.

EPSS over last 30 days · oldest: 0.008 · newest: 0.009 · change: +0.002

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

Frequently asked questions

What is CVE-2026-35031?
CVE-2026-35031 is a critical-severity vulnerability in Jellyfin, classified under Improper Input Validation. CVSS score: 9.9/10. Published 2026-04-14.
How severe is CVE-2026-35031?
Critical severity. CVSS v3 base score is 9.9 out of 10.
Is CVE-2026-35031 known to be exploited?
1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.