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Tinyauth: forward-auth per-app ACL is matched case-sensitively against the (case-insensitive) hostname, letting an authenticated user reach apps they are not on the allowlist for

Type: advisorySources: OSV

Tinyauth is an authentication and authorization server. Prior to 5.1.2, Tinyauth compares forwarded hostnames case-sensitively while reverse proxies route equivalent hostnames case-insensitively, allowing an authenticated low-privilege user to bypass per-app access controls with a differently cased hostname. The lookup in internal/service/access_controls_service.go through lookupStaticACLs and GetAccessControls, and the Docker-label fallback in internal/service/docker_service.go through GetLabels, can miss the configured app and return an empty access-control object. internal/controller/proxy_controller.go proxyHandler then treats the empty user, group, OAuth, LDAP, and IP restrictions as permissive and returns an authenticated result for an app that should exclude the user. Unauthenticated users remain subject to login, and global login-time allowlists are not bypassed. This issue is fixed in version 5.1.2.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-77560
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 01:36 UTC · Revision 1

Source evidence

Tinyauth: forward-auth per-app ACL is matched case-sensitively against the (case-insensitive) hostname, letting an authenticated user reach apps they are not on the allowlist for

core-osv · Original source

Published 21 Sept 2026, 16:39 UTC

Tinyauth is an authentication and authorization server. Prior to 5.1.2, Tinyauth compares forwarded hostnames case-sensitively while reverse proxies route equivalent hostnames case-insensitively, allowing an authenticated low-privilege user to bypass per-app access controls with a differently cased hostname. The lookup in internal/service/access_controls_service.go through lookupStaticACLs and GetAccessControls, and the Docker-label fallback in internal/service/docker_service.go through GetLabels, can miss the configured app and return an empty access-control object. internal/controller/proxy_controller.go proxyHandler then treats the empty user, group, OAuth, LDAP, and IP restrictions as permissive and returns an authenticated result for an app that should exclude the user. Unauthenticated users remain subject to login, and global login-time allowlists are not bypassed. This issue is fixed in version 5.1.2.

osv:CVE-2026-77560
Complete source record
{
  "id": "0a0c527349dc187359e40ac5e9f64dcc67c94a42defafa06e62dddc4f4b473a8",
  "url": "https://osv.dev/vulnerability/CVE-2026-77560",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Tinyauth: forward-auth per-app ACL is matched case-sensitively against the (case-insensitive) hostname, letting an authenticated user reach apps they are not on the allowlist for",
    "summary": "Tinyauth is an authentication and authorization server. Prior to 5.1.2, Tinyauth compares forwarded hostnames case-sensitively while reverse proxies route equivalent hostnames case-insensitively, allowing an authenticated low-privilege user to bypass per-app access controls with a differently cased hostname. The lookup in internal/service/access_controls_service.go through lookupStaticACLs and GetAccessControls, and the Docker-label fallback in internal/service/docker_service.go through GetLabels, can miss the configured app and return an empty access-control object. internal/controller/proxy_controller.go proxyHandler then treats the empty user, group, OAuth, LDAP, and IP restrictions as permissive and returns an authenticated result for an app that should exclude the user. Unauthenticated users remain subject to login, and global login-time allowlists are not bypassed. This issue is fixed in version 5.1.2.",
    "evidence": "osv:CVE-2026-77560",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-77560",
      "aliases": [
        "CVE-2026-77560",
        "GHSA-328g-jx67-v94g",
        "GO-2026-6552"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"
        }
      ],
      "affected": [
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              "events": [
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                {
                  "fixed": "c7077a7c845dc71f9cbab55dc15151920887881e"
                },
                {
                  "fixed": "80bc87188ec3aabc5104c249eaa7b997973b9275"
                },
                {
                  "fixed": "e75605b2c534ec83525a33603e16d76baca13399"
                }
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              "database_specific": {
                "extracted_events": [
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                    "range": [
                      {
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                      {
                        "fixed": "5.1.2"
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                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
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                    "source": "REFERENCES_COMMIT"
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                        "fixed": "c7077a7c845dc71f9cbab55dc15151920887881e"
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                    "source": "REFERENCES_TAG",
                    "original_tag": "v5.1.2"
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          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77560.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:48.850695588Z",
      "provider": "osv",
      "references": [
        "https://github.com/tinyauthapp/tinyauth/releases/tag/v5.1.2",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77560.json",
        "https://github.com/tinyauthapp/tinyauth/security/advisories/GHSA-328g-jx67-v94g",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-77560",
        "https://github.com/tinyauthapp/tinyauth/commit/80bc87188ec3aabc5104c249eaa7b997973b9275",
        "https://github.com/tinyauthapp/tinyauth/commit/e75605b2c534ec83525a33603e16d76baca13399",
        "https://github.com/tinyauthapp/tinyauth/pull/1000",
        "https://github.com/tinyauthapp/tinyauth/pull/1028"
      ],
      "provider_metadata": {
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          "CWE-636",
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        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77560.json"
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        "evidence": "/id"
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517033,
  "published_at": "2026-09-21T16:39:18.606+00:00"
}