CVE-2026-55164: Lemur Lemur User-update Path Stores Plaintext Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-q437-g7fv-2jvv",
  "modified" : "2026-06-25T22:02:12Z",
  "published" : "2026-06-25T22:02:12Z",
  "aliases" : [ "CVE-2026-55164" ],
  "summary" : "Lemur user-update path stores plaintext passwords",
  "details" : "## Summary\n\n`lemur.users.service.update()` writes a user's new password as plaintext to the `users.password` column. The `User` model wires bcrypt hashing to SQLAlchemy's `before_insert` event but registers no equivalent listener for `before_update`, and `service.update()` does not call `user.hash_password()` after assigning the new value. Every password change performed through the admin-gated `PUT /api/1/users/<id>` endpoint persists the user's password to the database in cleartext.\n\n## Root Cause\n\n`lemur/users/models.py`:\n\n```python\n# line 38\nclass User(BaseModel):\n    __tablename__ = \"users\"\n    id = Column(Integer, primary_key=True)\n    password = Column(String(128))            # plain column, no setter, no Vault descriptor\n\n# line 74\n    def hash_password(self):\n        if self.password:\n            self.password = bcrypt.generate_password_hash(self.password).decode(\"utf-8\")\n\n# line 111\nlisten(User, \"before_insert\", hash_password)  # only before_insert is wired\n```\n\n`lemur/users/service.py`:\n\n```python\n# line 46\ndef update(user_id, username, email, active, profile_picture, roles, password=None):\n    ...\n    user = get(user_id)\n    user.username = username\n    user.email = email\n    user.active = active\n    user.profile_picture = profile_picture\n    if password:\n        user.password = password              # raw assignment\n    update_roles(user, roles)\n    return database.update(user)              # commits, no hashing\n```\n\nNo `before_update` listener exists. `User.password` is a plain `Column(String(128))` with no property setter that hashes on assignment. The bcrypt code path is bypassed entirely on every UPDATE statement that touches this column.\n\n## Affected Endpoints\n\n| Method | Path | Source |\n|---|---|---|\n| PUT | /api/1/users/`<id>` | lemur/users/views.py:274 (gated by `@admin_permission.require`) |\n\n`lemur/auth/views.py:323` also calls `user_service.update()` during SSO/OAuth login, but passes only six positional arguments. `password` defaults to `None` on that path and the `if password:` guard short-circuits. The bug is triggered only through the admin-only PUT handler.\n\n## Impact\n\nWhen an administrator changes a user's password via `PUT /api/1/users/<id>`, the cleartext password is persisted to `users.password`. Subsequent login attempts for that user will fail (`check_password` calls `bcrypt.check_password_hash` against an unhashed value), pushing operators toward workarounds.\n\nThe more serious consequence is a defense-in-depth bypass. Bcrypt is the protection that prevents a database compromise from yielding usable credentials. With plaintext rows present, an attacker who exfiltrates the `users` table, a backup, a read replica, or query logs obtains directly usable login credentials — no offline cracking required. Because users reuse passwords across services, the blast radius extends beyond Lemur.\n\nThe bug specifically affects admin-driven password resets, which are the normal post-incident workflow and exactly when plaintext storage is most harmful.\n\n## Steps to Reproduce\n\n1. Install Lemur with default config. Create an admin user and a target user 'alice' (created via the standard flow, password will be hashed correctly on insert).\n\n2. Verify the initial hash:\n   psql lemur -c \"SELECT password FROM users WHERE username='alice';\"\n   # Output: $2b$12$N9Q...   (bcrypt hash, as expected)\n\n3. As admin, change alice's password via the API:\n   curl -X PUT https://lemur.local/api/1/users/<alice_id> \\\n        -H \"Authorization: Bearer <admin_jwt>\" \\\n        -H \"Content-Type: application/json\" \\\n        -d '{\n          \"username\": \"alice\",\n          \"email\": \"alice@example.com\",\n          \"active\": true,\n          \"profile_picture\": null,\n          \"roles\": [{\"name\": \"operator\"}],\n          \"password\": \"ProofOfConcept_2026\"\n        }'\n\n4. Read the column again:\n   psql lemur -c \"SELECT password FROM users WHERE username='alice';\"\n   # Output: ProofOfConcept_2026   ← plaintext, not hashed\n\n5. Confirm the failure mode: 'alice' can no longer log in with 'ProofOfConcept_2026'\n   because check_password runs bcrypt.check_password_hash() against the cleartext column.\n\n\n## Remediation\n\nRegister the listener for both events:\n\n```python\n# lemur/users/models.py\nlisten(User, \"before_insert\", hash_password)\nlisten(User, \"before_update\", hash_password)\n```\n\nAlternative, equivalent fix in the service layer:\n\n```python\n# lemur/users/service.py, in update()\n    if password:\n        user.password = password\n        user.hash_password()\n```\n\nThe listener fix is preferred because it closes the gap for any future code path that mutates `user.password`.\n\nA one-time migration is recommended to detect and re-hash any rows already stored in cleartext. Bcrypt hashes begin with `$2b$`, `$2a$`, or `$2y$`. Any cleartext credential should be treated as **compromised** — rotate it, do not just re-hash it — since it has been at rest in plaintext and may exist in backups, audit logs, and replicas.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "lemur"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.9.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.9.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/Netflix/lemur/security/advisories/GHSA-q437-g7fv-2jvv"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Netflix/lemur"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Netflix/lemur/releases/tag/v1.9.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-256" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-25T22:02:12Z",
    "nvd_published_at" : null
  }
}