{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": [
              "cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*",
              "cpe:2.3:a:traefik:traefik:3.7.0:ea1:*:*:*:*:*:*",
              "cpe:2.3:a:traefik:traefik:3.7.0:ea2:*:*:*:*:*:*",
              "cpe:2.3:a:traefik:traefik:3.7.0:ea3:*:*:*:*:*:*"
            ],
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.11.43"
              },
              {
                "introduced": "3.0.0"
              },
              {
                "fixed": "3.6.14"
              },
              {
                "introduced": "3.7.0-ea1"
              },
              {
                "last_affected": "3.7.0-ea1"
              },
              {
                "introduced": "3.7.0-ea2"
              },
              {
                "last_affected": "3.7.0-ea2"
              },
              {
                "introduced": "3.7.0-ea3"
              },
              {
                "last_affected": "3.7.0-ea3"
              }
            ],
            "source": [
              "CPE_RANGE",
              "CPE_STRING",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "a9ce32a8dc3db5170e283215ab000bd053aea865"
            },
            {
              "introduced": "d99d2f95e66a28ee8180634dc80fdf13ba68c62a"
            },
            {
              "fixed": "a6664c95b589842489d37d73e7d01bf1c8881685"
            },
            {
              "introduced": "67c64ed9b25fbb90f1086977a62827133a7aa01b"
            },
            {
              "fixed": "a47e15f1299d23fec1bcbb78bece4325a40d63f2"
            }
          ],
          "repo": "https://github.com/traefik/traefik",
          "type": "GIT"
        }
      ],
      "versions": [
        "3.7.0-ea1",
        "3.7.0-ea2",
        "3.7.0-ea3"
      ]
    }
  ],
  "aliases": [
    "GHSA-6x2q-h3cr-8j2h"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-208"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41263.json"
  },
  "details": "Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.43, 3.6.14, and 3.7.0-rc.2, there is a timing side-channel vulnerability in Traefik's BasicAuth middleware that allows an attacker to enumerate valid usernames through response-time differences. The variable intended to hold a constant-time fallback secret always resolves to an empty string, causing the constant-time comparison to short-circuit in microseconds rather than performing a full bcrypt evaluation. This restores the original timing oracle and makes it possible to distinguish existing users from non-existing ones by measuring authentication response times. This issue has been patched in versions 2.11.43, 3.6.14, and 3.7.0-rc.2.",
  "id": "CVE-2026-41263",
  "modified": "2026-08-12T03:51:19.701618396Z",
  "published": "2026-04-30T20:39:49.658Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/traefik/traefik/releases/tag/v2.11.43"
    },
    {
      "type": "WEB",
      "url": "https://github.com/traefik/traefik/releases/tag/v3.6.14"
    },
    {
      "type": "WEB",
      "url": "https://github.com/traefik/traefik/releases/tag/v3.7.0-rc.2"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/41xxx/CVE-2026-41263.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/traefik/traefik/security/advisories/GHSA-6x2q-h3cr-8j2h"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-41263"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Traefik: BasicAuth middleware: timing side-channel vulnerability"
}