Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Privileges required (PR:L) | Low privileges required |
| User interaction (UI:N) | No user interaction |
| Scope (S:C) | Scope changed: impact spreads beyond the component |
| Confidentiality (C:H) | High confidentiality impact |
| Integrity (I:H) | High integrity impact |
| Availability (A:H) | High availability impact |
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
About Jellyfin
CVE-2026-35031 affects Jellyfin, a product from Jellyfin. Before acting, confirm where Jellyfin runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: 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.
The weakness class is Improper Input Validation. The software trusts input without checking it is safe.
Based on its CVSS vector, the flaw can be reached over the network, needs some level of access, and needs no user interaction. Apply the vendor fix and confirm exposure on internet facing and business critical assets first.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | Jellyfin |
| Affected versions | Jellyfin before 10.11.7 |
| Published | Apr 14, 2026 |
| Last modified | Jul 24, 2026 |
| Added to CISA KEV | Not listed |
| Assigning CNA | security-advisories@github.com |
How to detect it
- Inventory every instance of Jellyfin and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of Jellyfin named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on Jellyfin to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Rank using EPSS and CVSS together with asset exposure and business impact. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
- CWE-20: Improper Input Validation More CVEs with this weakness
- CWE-22: Path Traversal More CVEs with this weakness
- CWE-187 More CVEs with this weakness
Technical References
Frequently asked questions
Related CVEs
Jellyfin is an open source self hosted media server. Versions prior to 10.11.7 contain an unauthenticated arbitrary file read vulnerability via ffmpeg argument injection through the StreamOptions query parameter parsing mechanism. The ParseStreamOptions method in StreamingHelpers.cs adds any lowercase query parameter to a dictionary without validation, bypassing the RegularExpression attribute on the level controller parameter, and the unsanitized value is concatenated directly into the ffmpeg command line. By injecting a drawtext filter with a textfile argument, an attacker can read arbitrary server files such as /etc/shadow and exfiltrate their contents as text rendered in the video stream response. The vulnerable /Videos/{itemId}/stream endpoint has no Authorize attribute, making this exploitable without authentication, though item GUIDs are pseudorandom and require an authenticated user to obtain. This issue has been fixed in version 10.11.7.
Jellyfin is an open source self hosted media server. Versions prior to 10.11.7 contain a vulnerability chain in the LiveTV M3U tuner endpoint (POST /LiveTv/TunerHosts), where the tuner URL is not validated, allowing local file read via non-HTTP paths and Server-Side Request Forgery (SSRF) via HTTP URLs. This is exploitable by any authenticated user because the EnableLiveTvManagement permission defaults to true for all new users. An attacker can chain these vulnerabilities by adding an M3U tuner pointing to an attacker-controlled server, serving a crafted M3U with a channel pointing to the Jellyfin database, exfiltrating the database to extract admin session tokens, and escalating to admin privileges. This issue has been fixed in version 10.11.7. If users are unable to upgrade immediately, they can disable Live TV Management privileges for all users.
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