{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "5.0.0-rc.10"
              },
              {
                "fixed": "5.0.0-rc.14"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "8fa0d9823fbef04aaab517e7ea0f4b17976f1502"
            },
            {
              "fixed": "fea75958a081ed337ceb578396174039694c48df"
            },
            {
              "fixed": "64530644f9b37ebb76ca14aeb83a77597a0034b7"
            },
            {
              "fixed": "73ad16e452670bbf843550a13361bd41e72ad964"
            }
          ],
          "repo": "https://github.com/team-alembic/ash_authentication",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-73j9-m294-fvv9"
  ],
  "database_specific": {
    "cna_assigner": "EEF",
    "cwe_ids": [
      "CWE-290"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91039.json",
    "unresolved_ranges": [
      {
        "extracted_events": [
          {
            "introduced": "64530644f9b37ebb76ca14aeb83a77597a0034b7"
          },
          {
            "fixed": "73ad16e452670bbf843550a13361bd41e72ad964"
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "details": "Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who operates one identity-provider connection of a dynamic_oidc strategy to be signed in as a local user established through a different connection.\n\nThe strategy is meant to keep each connection in its own identity namespace by writing every UserIdentity row's strategy field as \"\u003cname\u003e/\u003cconnection_id\u003e\", but that namespacing never takes effect. __connection_id__ is populated only on the ephemeral runtime struct built per request in dynamic_oidc/plug.ex, and DynamicOidc.IdentityChange.change/3 re-fetches the strategy from the compile-time DSL through Info.strategy_for_action, yielding the persisted struct whose __connection_id__ is its defstruct default of nil. OAuth2.identity_strategy_name/1 therefore falls back to the bare strategy name for both the identity write and the reads in oauth2/user_resolver.ex and oauth2/sign_in_preparation.ex. Since the identity resource's unique key is (uid, strategy), one row exists per sub across every connection, and the identity-match branch runs before any email check. Neither strategy handles iss, so nothing else distinguishes the issuers: OpenID Connect Core section 5.7 makes sub unique only within an issuer, so two connections numbering subjects independently share one subject space.\n\nThis issue affects ash_authentication: from 5.0.0-rc.10 before 5.0.0-rc.14.",
  "id": "CVE-2026-91039",
  "modified": "2026-09-20T11:30:34.910649684Z",
  "published": "2026-09-17T15:19:15.994Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-91039.html"
    },
    {
      "type": "WEB",
      "url": "https://github.com"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-91039"
    },
    {
      "type": "WEB",
      "url": "https://repo.hex.pm"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91039.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-73j9-m294-fvv9"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-91039"
    },
    {
      "type": "FIX",
      "url": "https://github.com/team-alembic/ash_authentication/commit/64530644f9b37ebb76ca14aeb83a77597a0034b7"
    },
    {
      "type": "FIX",
      "url": "https://github.com/team-alembic/ash_authentication/commit/73ad16e452670bbf843550a13361bd41e72ad964"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/team-alembic/ash_authentication"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "dynamic_oidc identities are not namespaced by connection in ash_authentication, allowing cross-connection account takeover"
}