CVE-2026-59218: Open WebUI Account Enumeration Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7rw5-9f7q-xj36",
  "modified" : "2026-07-24T16:55:06Z",
  "published" : "2026-07-24T16:55:06Z",
  "aliases" : [ "CVE-2026-59218" ],
  "summary" : "Open WebUI: Account enumeration via observable login timing discrepancy",
  "details" : "### Summary\n\nThe `/api/v1/auths/signin` endpoint leaked whether an email address belonged to a registered account through a response-time side channel. Password verification ran bcrypt only when the email was found in the database; for a non-existent email the request returned early without hashing. The expensive bcrypt comparison therefore made valid-account attempts respond significantly slower (~180 ms) than non-existent ones (~5 ms), so an unauthenticated attacker could enumerate valid accounts by measuring response time.\n\n### Details\n\nOn signin the backend looked the user up by email and only performed the bcrypt password comparison if a record existed. A missing email short-circuited before any hashing, producing the timing gap. The built-in brute-force throttling did not prevent it: sending one request at a time with a small delay between requests stays under the rate limit while still exposing the difference.\n\nObserved in the reporter's run (HTTP 400 for every attempt, the response time is the signal):\n\n```\nEmail                Status   Response time\njoe@example.com      400      186 ms   <- valid account\nlarry@example.com    400        9 ms\njose@example.com     400        6 ms\njames@example.com    400        5 ms\n```\n\n### Impact\n\nAn unauthenticated attacker can enumerate which email addresses are registered accounts, which enables targeted password-spraying against confirmed accounts. The impact is amplified by MFA not being enabled by default. No data is read or modified; the disclosure is limited to account existence.\n\n### Patched\n\nThe authentication path now runs a bcrypt verification against a constant placeholder hash whenever the email does not resolve to an active credential, so a real hash comparison executes on every attempt and the response time is the same whether or not the account exists. Fixed in 0.10.0.\n\n### Credits\n\n@dievus",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "open-webui"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.10.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/security/advisories/GHSA-7rw5-9f7q-xj36"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59218"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/pull/26385"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/commit/993e74912199c66c522f08ec81abe31d76985e39"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/open-webui/open-webui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/open-webui/open-webui/releases/tag/v0.10.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-208" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T16:55:06Z",
    "nvd_published_at" : "2026-07-09T17:17:02Z"
  }
}