CVE-2026-49757
Description
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.
Predictions
Heuristic predictions, AS-IS, for prioritization only.
Mitigations
No mitigations published for this CVE yet.
The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.
✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here withsource_tier=community-verified.
Package impact
| Ecosystem | Package | Vulnerable | Fixed |
|---|---|---|---|
| Hex | ash_authentication | >=0.1.0,<4.14.0||>=5.0.0-rc.0,<5.0.0-rc.10 | 4.14.0 |
References
- https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-777c-2fxx-qr28
- https://cna.erlef.org/cves/CVE-2026-49757.html
- https://github.com/team-alembic/ash_authentication/commit/728b8d28c1b5f465fa1116ef044a815300fc733d
- https://github.com/team-alembic/ash_authentication/commit/64530644f9b37ebb76ca14aeb83a77597a0034b7
- https://hex.pm/packages/ash_authentication
- https://osv.dev/vulnerability/EEF-CVE-2026-49757
CWEs
CWE-290
Community-verified mitigations for this CVE will appear above when contributors publish them.
Verify integrity in audit chain (admin only). AS-IS.