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Critical Severity Vulnerability

This vulnerability has been rated as Critical severity. Immediate action is recommended.

CVE-2026-35031

Critical

Low Medium High Critical

9.9

CVSS Score

Published: Apr 14, 2026

Last Modified: Apr 17, 2026

CWE: CWE-20

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 Metrics

Common Vulnerability Scoring System

Vector String:

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Scope

Confidentiality

Integrity

Availability

References & Resources

Severity Details

9.9

out of 10.0

Critical

Weakness Type (CWE)

CWE-20 Top 25 #14

Improper Input Validation

Description: The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Exploit Likelihood: High
Typical Severity: High
Abstraction Level: Class