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Medium

Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service

Type: advisorySources: OSV

Tinyauth is an authentication and authorization server. Prior to 5.1.0, an unauthenticated remote attacker can send POST /api/user/login requests with 257 distinct nonexistent usernames to fill MaxLoginAttemptRecords and activate a global login lockdown. internal/controller/user_controller.go loginHandler passes each attacker-controlled identifier to internal/service/auth_service.go RecordLoginAttempt, which invokes lockdownMode after the map reaches its cap. IsAccountLocked checks that global state before validating unrelated accounts, causing valid users to receive HTTP 429 until auth.loginTimeout expires, approximately 300 seconds by default. The attack can be repeated, but existing authenticated sessions are not invalidated. This issue is fixed in version 5.1.0.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-77561
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 16:22 UTC · Revision 1

Source evidence

Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service

core-osv · Original source

Published 21 Sept 2026, 16:48 UTC

Tinyauth is an authentication and authorization server. Prior to 5.1.0, an unauthenticated remote attacker can send POST /api/user/login requests with 257 distinct nonexistent usernames to fill MaxLoginAttemptRecords and activate a global login lockdown. internal/controller/user_controller.go loginHandler passes each attacker-controlled identifier to internal/service/auth_service.go RecordLoginAttempt, which invokes lockdownMode after the map reaches its cap. IsAccountLocked checks that global state before validating unrelated accounts, causing valid users to receive HTTP 429 until auth.loginTimeout expires, approximately 300 seconds by default. The attack can be repeated, but existing authenticated sessions are not invalidated. This issue is fixed in version 5.1.0.

osv:CVE-2026-77561
Complete source record
{
  "id": "9b4fa0612dc26a599670dac34f125c18d5c69b4634f576bfa6f350c7a68defa5",
  "url": "https://osv.dev/vulnerability/CVE-2026-77561",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Tinyauth: Unauthenticated login attempts can trigger global login lockdown denial of service",
    "summary": "Tinyauth is an authentication and authorization server. Prior to 5.1.0, an unauthenticated remote attacker can send POST /api/user/login requests with 257 distinct nonexistent usernames to fill MaxLoginAttemptRecords and activate a global login lockdown. internal/controller/user_controller.go loginHandler passes each attacker-controlled identifier to internal/service/auth_service.go RecordLoginAttempt, which invokes lockdownMode after the map reaches its cap. IsAccountLocked checks that global state before validating unrelated accounts, causing valid users to receive HTTP 429 until auth.loginTimeout expires, approximately 300 seconds by default. The attack can be repeated, but existing authenticated sessions are not invalidated. This issue is fixed in version 5.1.0.",
    "evidence": "osv:CVE-2026-77561",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-77561",
      "aliases": [
        "CVE-2026-77561",
        "GHSA-9xhm-w3wj-xhqh",
        "GO-2026-6564"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/tinyauthapp/tinyauth",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "9eabfe89fdecc030c33054eaad6c998bf55661fb"
                },
                {
                  "fixed": "654b5cc436fc67865c1f55edf9ba9fbded50b74f"
                },
                {
                  "fixed": "dade1e2c8f27a23df56ac216dcaf4b37081698e7"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "5.1.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "654b5cc436fc67865c1f55edf9ba9fbded50b74f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "dade1e2c8f27a23df56ac216dcaf4b37081698e7"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "9eabfe89fdecc030c33054eaad6c998bf55661fb"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v5.1.0"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.1.0-alpha.1",
            "v5.0.7",
            "v5.0.7-beta.1",
            "v5.0.7-alpha.1",
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            "v4.0.1-beta.1",
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            "v3.3.1",
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            "v3.3.0-alpha.2",
            "v3.3.0-alpha.1",
            "v3.2.1",
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            "v3.2.0",
            "v3.2.0-beta.5",
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77561.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.168440580Z",
      "provider": "osv",
      "references": [
        "https://github.com/tinyauthapp/tinyauth/releases/tag/v5.1.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77561.json",
        "https://github.com/tinyauthapp/tinyauth/security/advisories/GHSA-9xhm-w3wj-xhqh",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-77561",
        "https://github.com/tinyauthapp/tinyauth/commit/654b5cc436fc67865c1f55edf9ba9fbded50b74f",
        "https://github.com/tinyauthapp/tinyauth/commit/dade1e2c8f27a23df56ac216dcaf4b37081698e7",
        "https://github.com/tinyauthapp/tinyauth/pull/1008",
        "https://github.com/tinyauthapp/tinyauth/pull/943"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-307"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77561.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-77561",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 519863,
  "published_at": "2026-09-21T16:48:21.732+00:00"
}