CVE-2026-44551: Open webui Authentication Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2r4p-jpmg-48f4",
  "modified" : "2026-05-15T23:52:10Z",
  "published" : "2026-05-08T19:38:31Z",
  "aliases" : [ "CVE-2026-44551" ],
  "summary" : "Open WebUI has an LDAP Empty Password Authentication Bypass",
  "details" : "# LDAP Empty Password Authentication Bypass\n\n## Affected Component\n\nLDAP authentication endpoint:\n- `backend/open_webui/routers/auths.py` (lines 468-477, user bind with empty password)\n- `backend/open_webui/models/auths.py` (lines 58-60, `LdapForm` model)\n\n## Affected Versions\n\nCurrent main branch (commit `6fdd19bf1`) and likely all versions with LDAP authentication support.\n\n## Description\n\nThe LDAP authentication endpoint does not validate that the submitted password is non-empty before performing a Simple Bind against the LDAP server. Per RFC 4513 Section 5.1.2, a Simple Bind with a valid DN and an empty password constitutes an \"unauthenticated simple authentication\" — many LDAP servers (including OpenLDAP in default configuration and some Active Directory setups) return success (resultCode 0) for this operation.\n\nThe `LdapForm` Pydantic model accepts `password: str` with no minimum length constraint, so an empty string passes validation. The subsequent `Connection.bind()` call succeeds on vulnerable LDAP servers, and the application issues a full session token for the target user.\n\n```python\n# models/auths.py:58-60 — no min_length on password\nclass LdapForm(BaseModel):\n    user: str\n    password: str\n\n# auths.py:469-477 — empty password reaches LDAP bind\nconnection_user = Connection(\n    server,\n    user_dn,\n    form_data.password,    # can be \"\"\n    auto_bind='NONE',\n    authentication='SIMPLE',\n)\nif not await asyncio.to_thread(connection_user.bind):\n    raise HTTPException(400, 'Authentication failed.')\n\n# If bind succeeds (which it does with empty password on many servers),\n# execution continues and a full session token is issued\n```\n\n## CVSS 3.1 Breakdown\n\n| Metric | Value | Rationale |\n|--------|-------|-----------|\n| Attack Vector | Network (N) | Exploited remotely via the LDAP login endpoint |\n| Attack Complexity | Low (L) | Single request with an empty password field |\n| Privileges Required | None (N) | No prior authentication needed |\n| User Interaction | None (N) | No victim interaction required |\n| Scope | Unchanged (U) | Impact within the application's authentication boundary |\n| Confidentiality | High (H) | Full access to victim's account data — chats, files, API keys, settings |\n| Integrity | High (H) | Can modify victim's data, settings, send messages as victim |\n| Availability | None (N) | No direct denial of service |\n\n## Attack Scenario\n\n1. LDAP authentication is enabled on the Open WebUI instance.\n2. The underlying LDAP server accepts unauthenticated simple binds (OpenLDAP default, some AD configs).\n3. Attacker sends:\n   ```\n   POST /api/v1/auths/ldap\n   {\"user\": \"admin_username\", \"password\": \"\"}\n   ```\n4. The app DN bind succeeds normally (line 366), finds the target user via LDAP search.\n5. The user bind (line 469-477) sends a Simple Bind with the target's DN and an empty password.\n6. The LDAP server returns success for the unauthenticated bind.\n7. `authenticate_user_by_email` (line 507) issues a full session token for the target user.\n8. Attacker has complete access to the victim's account.\n\n## Impact\n\n- Complete authentication bypass — any LDAP user account can be taken over without knowing the password\n- Includes admin accounts if they authenticate via LDAP\n- No rate limiting on the LDAP endpoint (unlike the password signin endpoint)\n- Zero interaction required from the victim\n\n## Preconditions\n\n- LDAP must be enabled (`ENABLE_LDAP=True`, disabled by default)\n- The LDAP server must accept unauthenticated simple binds with empty passwords (OpenLDAP default behavior, configurable on AD)\n- Attacker must know a valid LDAP username",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "open-webui"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.9.0"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 0.8.12"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/security/advisories/GHSA-2r4p-jpmg-48f4"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44551"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/open-webui/open-webui"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-08T19:38:31Z",
    "nvd_published_at" : "2026-05-15T20:16:46Z"
  }
}