CVE-2026-49757

Authentication Bypass by Spoofing vulnerability in team-alembic AshAuthentication allows account takeover of local users via OAuth2/OIDC sign-in. AshAuthentication's OAuth2 and OIDC family strategies matched the local user by email address (an upsert on the email field, or a user-defined sign-in filter) rather than by the OpenID Connect iss/sub claim combination. Per OpenID Connect Core §5.7, only iss/sub uniquely and stably identifies an end-user; other claims, including email, MUST NOT be used as unique identifiers. A provider login presenting a victim's email, including an unverified email, a reused email, or an account with email_verified: false, resolved to and signed in as the victim's existing local account. An unauthenticated attacker who can register an account on any accepted OAuth provider with the victim's email (or who benefits from provider-side email reuse or reclamation) obtains the victim's full local privileges. The fix resolves users by the (strategy, sub) identity stored in a user identity resource, and only links a new sub to an existing local account by email when the provider's email_verified claim is trusted (trust_email_verified?). This issue affects ash_authentication from 0.1.0 before 4.14.0 and from 5.0.0-rc.0 before 5.0.0-rc.10.

CVSS

No CVSS.

References

Link	Resource
https://cna.erlef.org/cves/CVE-2026-49757.html
https://github.com/team-alembic/ash_authentication/commit/64530644f9b37ebb76ca14aeb83a77597a0034b7
https://github.com/team-alembic/ash_authentication/commit/728b8d28c1b5f465fa1116ef044a815300fc733d
https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-777c-2fxx-qr28
https://osv.dev/vulnerability/EEF-CVE-2026-49757

Configurations

No configuration.

History

15 Jun 2026, 12:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-06-15 12:16

Updated : 2026-06-17 10:55

NVD link : CVE-2026-49757

Mitre link : CVE-2026-49757

CVE.ORG link : CVE-2026-49757

JSON object : View

Products Affected

No product.

CWE

CWE-290

Authentication Bypass by Spoofing

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"https://github.com", "defaultStatus": "unaffected", "programRoutines": [{"name": "'Elixir.AshAuthentication.Strategy.OAuth2.IdentityChange':change/3"}, {"name": "'Elixir.AshAuthentication.Strategy.OAuth2.SignInPreparation':prepare/3"}]}]}], "published": "2026-06-15T12:16:25.777", "references": [{"url": "https://cna.erlef.org/cves/CVE-2026-49757.html", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/team-alembic/ash_authentication/commit/64530644f9b37ebb76ca14aeb83a77597a0034b7", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/team-alembic/ash_authentication/commit/728b8d28c1b5f465fa1116ef044a815300fc733d", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-777c-2fxx-qr28", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}, {"url": "https://osv.dev/vulnerability/EEF-CVE-2026-49757", "source": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}], 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Per OpenID Connect Core \u00a75.7, only iss/sub uniquely and stably identifies an end-user; other claims, including email, MUST NOT be used as unique identifiers.\n\nA provider login presenting a victim's email, including an unverified email, a reused email, or an account with email_verified: false, resolved to and signed in as the victim's existing local account. An unauthenticated attacker who can register an account on any accepted OAuth provider with the victim's email (or who benefits from provider-side email reuse or reclamation) obtains the victim's full local privileges.\n\nThe fix resolves users by the (strategy, sub) identity stored in a user identity resource, and only links a new sub to an existing local account by email when the provider's email_verified claim is trusted (trust_email_verified?).\n\nThis issue affects ash_authentication from 0.1.0 before 4.14.0 and from 5.0.0-rc.0 before 5.0.0-rc.10."}], "lastModified": "2026-06-17T10:55:44.140", "sourceIdentifier": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}