yutu: Arbitrary File Write via MCP caption-download Tool

Exploitation

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

CVSS

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

EPSS

• CVE-2026-50158: 0.23% estimated exploitation activity in the next 30 days; percentile 13.75 (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.

Arbitrary File Write via MCP caption-download Tool Summary The caption-download MCP tool in yutu passes the caller-supplied file parameter directly to os.Create() at pkg/caption/caption.go:272 without any path validation, canonicalization, or confinement to the pkg.Root boundary (YUTUROOT). A local attacker — or any process able to reach the HTTP MCP server — can write arbitrary content to any path writable by the yutu process, entirely outside the intended working directory. This is a High severity vulnerability (CVSS 7.7) with high integrity and availability impact. Details yutu uses pkg.Root (backed by Go 1.24's os.OpenRoot) to restrict all file I/O to the YUTUROOT directory. Every other caption file-write path honours this boundary: | Method | Sink | Confined? | |--------|------|-----------| | Caption.Insert() | pkg.Root.Open(c.File) (caption.go:109) | Yes | | Caption.Update() | pkg.Root.Open(c.File) (caption.go:193) | Yes | | Caption.Download() | os.Create(c.File)…

Published by the source

14 Jul 2026, 19:34 UTC

Last modified by the source

14 Jul 2026, 19:34 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2c7f-fxww-6w6c

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# Patch Next advisory brief: CVE-2026-50158

Advisory: yutu: Arbitrary File Write via MCP `caption-download` Tool
IDs: CVE-2026-50158, GHSA-2c7f-fxww-6w6c
Record: https://patchnext.com/advisories/cve-2026-50158 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/eat-pray-ai/yutu 0.10.9-dev1. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/eat-pray-ai/yutu: affected < 0.10.9-dev1; fixed in 0.10.9-dev1

## Suggested inspection (read-only)
- Go github.com/eat-pray-ai/yutu: 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 github.com/eat-pray-ai/yutu.
- 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-2c7f-fxww-6w6c (GitHub-reviewed advisory GHSA-2c7f-fxww-6w6c lists affected ranges: Go github.com/eat-pray-ai/yutu >=0 <0.10.9-dev1)

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