Authentication bypass via second StartupMessage during SCRAM authentication in PgBouncer

{
  "id": "9c77242d7f853f1bb6c070e9518bd9a6d04466cf344441dcaf95a280df8e9f68",
  "url": "https://osv.dev/vulnerability/BIT-pgbouncer-2026-107350",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Authentication bypass via second StartupMessage during SCRAM authentication in PgBouncer",
    "summary": "Improper authentication in PgBouncer 1.17.0 through 1.26.0 allows a remote attacker who knows the password of a user listed in auth_file to log in as any other user that authenticates using SCRAM, including PgBouncer admin users and backend superusers. A second StartupMessage sent during SCRAM authentication against a non-existent database is not rejected and switches the user being logged in as, while the SCRAM exchange is still verified against the keys of the first user.",
    "evidence": "osv:BIT-pgbouncer-2026-107350",
    "products": [
      {
        "name": {
          "value": "pgbouncer",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.26.1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": []
      }
    ],
    "severity": "high",
    "structured": {
      "id": "BIT-pgbouncer-2026-107350",
      "aliases": [
        "BIT-pgbouncer-2026-107350",
        "CVE-2026-107350"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "SEMVER",
              "events": [
                {
                  "introduced": "1.17.0"
                },
                {
                  "fixed": "1.26.1"
                }
              ]
            }
          ],
          "package": {
            "name": "pgbouncer",
            "purl": "pkg:bitnami/pgbouncer",
            "ecosystem": "Bitnami"
          },
          "severity": [
            {
              "type": "CVSS_V3",
              "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
            }
          ],
          "database_specific": {
            "source": "https://github.com/bitnami/vulndb/tree/main/data/pgbouncer/BIT-pgbouncer-2026-107350.json"
          }
        }
      ],
      "modified": "2026-10-21T12:00:38.504517994Z",
      "provider": "osv",
      "references": [
        "https://nvd.nist.gov/vuln/detail/CVE-2026-107350",
        "https://www.pgbouncer.org/changelog.html"
      ],
      "provider_metadata": {
        "cpes": [
          "cpe:2.3:a:pgbouncer:pgbouncer:*:*:*:*:*:*:*:*"
        ],
        "severity": "High"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-107350",
        "evidence": "/aliases"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/database_specific/severity"
  },
  "source_id": "core-osv",
  "document_id": 393022,
  "published_at": "2026-10-21T08:55:11.42+00:00"
}