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CVE-2026-50158

yutu: Arbitrary File Write via MCP `caption-download` Tool

7.7 HighFix available

yutu is an AI-powered toolkit for managing and growing YouTube channels. Prior to 0.10.9, the caption-download MCP tool accepts a caller-controlled file parameter through cmd/caption/download.go and passes it to Caption.Download() in pkg/caption/caption.go, where os.Create() creates or truncates that path without using the pkg.Root confinement boundary backed by YUTU_ROOT. A principal able to invoke caption-download, including a local HTTP client when the MCP server runs with its default authentication-disabled configuration, can write downloaded caption bytes to any path writable by the yutu process outside YUTU_ROOT. This can overwrite application files, configuration, shell startup files, logs, or data and can cause persistent code execution or denial of service depending on the selected writable target. Live caption retrieval also requires usable service credentials and an accessible caption identifier. This issue is fixed in version 0.10.9.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
High
Availability
High

Exploit likelihood

0.23%Up 0.1 points since Sep 18, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.7

yutu: Arbitrary File Write via MCP `caption-download` Tool

yutu is an AI-powered toolkit for managing and growing YouTube channels. Prior to 0.10.9, the caption-download MCP tool accepts a caller-controlled file parameter through cmd/caption/download.go and passes it to Caption.Download() in pkg/caption/caption.go, where os.Create() creates or truncates that path without using the pkg.Root confinement boundary backed by YUTU_ROOT. A principal able to invoke caption-download, including a local HTTP client when the MCP server runs with its default authentication-disabled configuration, can write downloaded caption bytes to any path writable by the yutu process outside YUTU_ROOT. This can overwrite application files, configuration, shell startup files, logs, or data and can cause persistent code execution or denial of service depending on the selected writable target. Live caption retrieval also requires usable service credentials and an accessible caption identifier. This issue is fixed in version 0.10.9.

Record
CVE-2026-50158
CVSS 3.1
7.7 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-73
Updated
2026-11-02
EUVDEUVD-2026-82566 7.7

yutu is an AI-powered toolkit for managing and growing YouTube channels. Prior to 0.10.9, the caption-download MCP tool accepts a caller-controlled file parameter through cmd/caption/download.go and passes it to Caption.Download() in pkg/caption/caption.go, where os.Create() creates or truncates that path without using the pkg.Root confinement boundary backed by YUTU_ROOT. A principal able to invoke caption-download, including a local HTTP client when the MCP server runs with its default authentication-disabled configuration, can write downloaded caption bytes to any path writable by the yutu process outside YUTU_ROOT. This can overwrite application files, configuration, shell startup files, logs, or data and can cause persistent code execution or denial of service depending on the selected writable target. Live caption retrieval also requires usable service credentials and an accessible caption identifier. This issue is fixed in version 0.10.9.

Record
EUVD-2026-82566
CVSS 3.1
7.7 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-2c7f-fxww-6w6c 7.7

yutu: Arbitrary File Write via MCP `caption-download` Tool

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 (YUTU_ROOT). 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 YUTU_ROOT 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) (caption.go:272) | No |

Caption.Download() is the sole outlier. The attacker-controlled file field flows without restriction from the MCP tool input schema to a raw os.Create() call:

  1. Source — cmd/caption/download.go:32–41: downloadInSchema declares file as a required string field in the MCP JSON input schema.
  2. Binding — cmd/caption/download.go:61–64: cobramcp.GenToolHandler maps MCP input to input.Download(writer).
  3. Sink — pkg/caption/caption.go:272: os.Create(c.File) creates or truncates the file at the attacker-supplied path.
  4. Write — pkg/caption/caption.go:280: file.Write(body) writes the downloaded caption bytes to that path.
// cmd/caption/download.go
var downloadInSchema = &jsonschema.Schema{
    Required: []string{"ids", "file"},          // line 34
    // ...
    "file": {Type: "string", Description: fileUsage},  // line 40
}

// cobramcp.GenToolHandler binds MCP → handler (line 61-64)
cobramcp.GenToolHandler(downloadTool, func(input caption.Caption, writer io.Writer) error {
    return input.Download(writer)
})

// pkg/caption/caption.go
body, err := io.ReadAll(res.Body)   // line 267
file, err := os.Create(c.File)      // line 272  ← unconfined sink
// ...
_, err = file.Write(body)           // line 280

The caption-download tool is registered by default in init() at cmd/caption/download.go:52, and the HTTP MCP server starts with --auth defaulting to false (cmd/mcp.go:42), meaning no authentication is required for local HTTP callers.

Recommended fix:

--- a/pkg/caption/caption.go
+++ b/pkg/caption/caption.go
@@
-       file, err := os.Create(c.File)
+       file, err := pkg.Root.OpenFile(c.File, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
        if err != nil {
                return errors.Join(errDownloadCaption, err)
        }

PoC

Prerequisites:

  • yutu 0.0.0-dev / commit 351c99d
  • Valid YUTU_CREDENTIAL and YUTU_CACHE_TOKEN available
  • yutu MCP server running in HTTP mode

Docker-based reproduction (no live credentials needed):

The self-contained PoC builds a binary that exercises caption.Download() directly inside a container, with YUTU_ROOT=/tmp/yutu_safe_root as the confinement boundary.

# From the report workspace root:
docker build --no-cache -t yutu-vuln001-poc \
    -f vuln-001/Dockerfile \
    reports/mcp_49_eat-pray-ai__yutu

docker run --rm yutu-vuln001-poc

Expected output confirms:

  • pkg.Root.Open("/tmp/poc-arbitrary-write.txt") is correctly rejected with path escapes from parent (control).
  • caption.Download() with file="/tmp/poc-arbitrary-write.txt" succeeds and creates a 79-byte file outside YUTU_ROOT (exploit).

Live MCP server reproduction:

# Start the HTTP MCP server (no auth by default)
yutu mcp --mode http --port 8216

# Initialise session
curl -sD /tmp/yutu.headers \
  -H 'Content-Type:…
Record
GHSA-2c7f-fxww-6w6c
CVSS 3.1
7.7 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-73
Updated
2026-11-02
NVD 7.7

yutu is an AI-powered toolkit for managing and growing YouTube channels. Prior to 0.10.9, the caption-download MCP tool accepts a caller-controlled file parameter through cmd/caption/download.go and passes it to Caption.Download() in pkg/caption/caption.go, where os.Create() creates or truncates that path without using the pkg.Root confinement boundary backed by YUTU_ROOT. A principal able to invoke caption-download, including a local HTTP client when the MCP server runs with its default authentication-disabled configuration, can write downloaded caption bytes to any path writable by the yutu process outside YUTU_ROOT. This can overwrite application files, configuration, shell startup files, logs, or data and can cause persistent code execution or denial of service depending on the selected writable target. Live caption retrieval also requires usable service credentials and an accessible caption identifier. This issue is fixed in version 0.10.9.

Record
CVE-2026-50158
CVSS 3.1
7.7 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-73
Updated
2026-11-02
OSV 7.7

yutu: Arbitrary File Write via MCP `caption-download` Tool

yutu is an AI-powered toolkit for managing and growing YouTube channels. Prior to 0.10.9, the caption-download MCP tool accepts a caller-controlled file parameter through cmd/caption/download.go and passes it to Caption.Download() in pkg/caption/caption.go, where os.Create() creates or truncates that path without using the pkg.Root confinement boundary backed by YUTU_ROOT. A principal able to invoke caption-download, including a local HTTP client when the MCP server runs with its default authentication-disabled configuration, can write downloaded caption bytes to any path writable by the yutu process outside YUTU_ROOT. This can overwrite application files, configuration, shell startup files, logs, or data and can cause persistent code execution or denial of service depending on the selected writable target. Live caption retrieval also requires usable service credentials and an accessible caption identifier. This issue is fixed in version 0.10.9.

Record
CVE-2026-50158
CVSS 3.1
7.7 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-73
Updated
2026-11-02
OSVGHSA-2c7f-fxww-6w6c 7.7

yutu: Arbitrary File Write via MCP `caption-download` Tool

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 (YUTU_ROOT). 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 YUTU_ROOT 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) (caption.go:272) | No |

Caption.Download() is the sole outlier. The attacker-controlled file field flows without restriction from the MCP tool input schema to a raw os.Create() call:

  1. Source — cmd/caption/download.go:32–41: downloadInSchema declares file as a required string field in the MCP JSON input schema.
  2. Binding — cmd/caption/download.go:61–64: cobramcp.GenToolHandler maps MCP input to input.Download(writer).
  3. Sink — pkg/caption/caption.go:272: os.Create(c.File) creates or truncates the file at the attacker-supplied path.
  4. Write — pkg/caption/caption.go:280: file.Write(body) writes the downloaded caption bytes to that path.
// cmd/caption/download.go
var downloadInSchema = &jsonschema.Schema{
    Required: []string{"ids", "file"},          // line 34
    // ...
    "file": {Type: "string", Description: fileUsage},  // line 40
}

// cobramcp.GenToolHandler binds MCP → handler (line 61-64)
cobramcp.GenToolHandler(downloadTool, func(input caption.Caption, writer io.Writer) error {
    return input.Download(writer)
})

// pkg/caption/caption.go
body, err := io.ReadAll(res.Body)   // line 267
file, err := os.Create(c.File)      // line 272  ← unconfined sink
// ...
_, err = file.Write(body)           // line 280

The caption-download tool is registered by default in init() at cmd/caption/download.go:52, and the HTTP MCP server starts with --auth defaulting to false (cmd/mcp.go:42), meaning no authentication is required for local HTTP callers.

Recommended fix:

--- a/pkg/caption/caption.go
+++ b/pkg/caption/caption.go
@@
-       file, err := os.Create(c.File)
+       file, err := pkg.Root.OpenFile(c.File, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0600)
        if err != nil {
                return errors.Join(errDownloadCaption, err)
        }

PoC

Prerequisites:

  • yutu 0.0.0-dev / commit 351c99d
  • Valid YUTU_CREDENTIAL and YUTU_CACHE_TOKEN available
  • yutu MCP server running in HTTP mode

Docker-based reproduction (no live credentials needed):

The self-contained PoC builds a binary that exercises caption.Download() directly inside a container, with YUTU_ROOT=/tmp/yutu_safe_root as the confinement boundary.

# From the report workspace root:
docker build --no-cache -t yutu-vuln001-poc \
    -f vuln-001/Dockerfile \
    reports/mcp_49_eat-pray-ai__yutu

docker run --rm yutu-vuln001-poc

Expected output confirms:

  • pkg.Root.Open("/tmp/poc-arbitrary-write.txt") is correctly rejected with path escapes from parent (control).
  • caption.Download() with file="/tmp/poc-arbitrary-write.txt" succeeds and creates a 79-byte file outside YUTU_ROOT (exploit).

Live MCP server reproduction:

# Start the HTTP MCP server (no auth by default)
yutu mcp --mode http --port 8216

# Initialise session
curl -sD /tmp/yutu.headers \
  -H 'Content-Type:…
Record
GHSA-2c7f-fxww-6w6c
CVSS 3.1
7.7 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Weakness
CWE-73
Updated
2026-11-02
OSVGO-2026-5980 No score

yutu: Arbitrary File Write via MCP `caption-download` Tool in github.com/eat-pray-ai/yutu

yutu: Arbitrary File Write via MCP caption-download Tool in github.com/eat-pray-ai/yutu

Record
GO-2026-5980
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/eat-pray-ai/yutu
Go
 before 0.10.9-dev1
0.10.9-dev1
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-50158 is a high vulnerability (CVSS 7.7) in Eat-pray-ai Yutu, published July 14, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.23%, the 13th percentile. Fixed in github.com/eat-pray-ai/yutu 0.10.9-dev1.

References

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