Directory traversal + file write causing arbitrary code execution

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2023-30626: 1.97% estimated exploitation activity in the next 30 days; percentile 80.45 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Frederic Linn (@FredericLinn) has reported a series of vulnerabilities that can result in directory traversal, file write, and potential remote code execution on Jellyfin instances. The general process involves chaining several exploits including a stored XSS vulnerability and can be used by an unprivileged user. The general process is (using the example of setting an intro video as the payload): Create a session as a low-priviledged user with a crafted authorization header Upload an executable that contains a malicious plugin inline via /ClientLog/Document (Admin hovers over our device in dashboard - XSS payload gets triggered) XSS Payload tries to set encoder path to our uploaded "log" file via /System/MediaEncoder/Path The request fails, but in the process our executable actually runs (I guess for verifying if the path points to a valid ffmpeg version) The executable will create a plugin folder and place the inlined plugin DLL inside it The XSS payload shuts down the server…

Published by the source

24 Apr 2023, 22:39 UTC

Last modified by the source

7 Nov 2023, 05:05 UTC

Source last checked

26 Oct 2026, 17:00 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9p5f-5x8v-x65m

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# Patch Next advisory brief: CVE-2023-30626

Advisory: Directory traversal + file write causing arbitrary code execution
IDs: CVE-2023-30626, GHSA-9p5f-5x8v-x65m
Record: https://patchnext.com/advisories/cve-2023-30626 (revision 1, source checked 26 Oct 2026, 17:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jellyfin.controller 10.8.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet jellyfin.controller: affected >= 10.8.0, < 10.8.10; fixed in 10.8.10

## Suggested inspection (read-only)
- NuGet jellyfin.controller: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on jellyfin.controller.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-9p5f-5x8v-x65m (GitHub-reviewed advisory GHSA-9p5f-5x8v-x65m lists affected ranges: NuGet jellyfin.controller >=10.8.0 <10.8.10)

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