Vulnerability advisory

EEF-CVE-2026-49757

OAuth2/OIDC account takeover in AshAuthentication via email-based user matching

Published Jun 15, 2026Updated Jul 30, 2026OSV record ↗

Also known as CVE-2026-49757GHSA-777c-2fxx-qr28

Severity

CVSS 4.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Affected versions

ash_authentication Hex

All ash_authentication advisories →

Affected	Fixed in
`0.1.0` to before 4.14.0	`4.14.0`Advisories →
`5.0.0-rc.0` to before 5.0.0-rc.10	`5.0.0-rc.10`Advisories →
Also listed as affected (161) `3.0.3` `3.1.0` `3.10.0` `3.10.1` `3.10.2` `3.10.3` `3.10.4` `3.10.5` `3.10.6` `3.10.7` `3.10.8` `3.11.0` `3.11.1` `3.11.10` `3.11.11` `3.11.12` `3.11.13` `3.11.14` `3.11.15` `3.11.16` `3.11.2` `3.11.3` `3.11.4` `3.11.5` `3.11.6` `3.11.7` `3.11.8` `3.11.9` `3.12.0` `3.12.1` `3.12.2` `3.12.3` `3.12.4` `3.2.0` `3.2.1` `3.2.2` `3.3.0` `3.3.1` `3.5.0` `3.5.1` `3.5.2` `3.5.3` `3.6.0` `3.6.1` `3.7.0` `3.7.1` `3.7.2` `3.7.3` `3.7.4` `3.7.5` `3.7.6` `3.7.8` `3.7.9` `3.8.0` `3.9.0` `3.9.1` `3.9.2` `3.9.3` `3.9.4` `3.9.5` `3.9.6` `4.0.0` `4.0.0-rc.0` `4.0.0-rc.1` `4.0.0-rc.2` `4.0.0-rc.3` `4.0.0-rc.5` `4.0.0-rc.6` `4.0.1` `4.0.2` `4.0.3` `4.0.4` `4.1.0` `4.10.0` `4.11.0` `4.12.0` `4.13.0` `4.13.1` `4.13.2` `4.13.3` `4.13.4` `4.13.5` `4.13.6` `4.13.7` `4.2.0` `4.2.1` `4.2.2` `4.2.3` `4.2.4` `4.2.5` `4.2.6` `4.2.7` `4.3.0` `4.3.1` `4.3.10` `4.3.11` `4.3.12` `4.3.2` `4.3.3` `4.3.4` `4.3.5` `4.3.6` `4.3.7` `4.3.8` `4.3.9` `4.4.0` `4.4.1` `4.4.2` `4.4.3` `4.4.4` `4.4.5` `4.4.6` `4.4.7` `4.4.8` `4.4.9` `4.5.0` `4.5.1` `4.5.2` `4.5.3` `4.5.4` `4.5.5` `4.5.6` `4.6.0` `4.6.1` `4.6.2` `4.6.3` `4.6.4` `4.7.0` `4.7.1` `4.7.2` `4.7.3` `4.7.4` `4.7.5` `4.7.6` `4.8.0` `4.8.1` `4.8.2` `4.8.3` `4.8.5` `4.8.6` `4.8.7` `4.9.0` `4.9.1` `4.9.2` `4.9.3` `4.9.4` `4.9.5` `4.9.6` `4.9.7` `4.9.8` `4.9.9` `5.0.0-rc.0` `5.0.0-rc.1` `5.0.0-rc.2` `5.0.0-rc.3` `5.0.0-rc.4` `5.0.0-rc.5` `5.0.0-rc.6` `5.0.0-rc.7` `5.0.0-rc.8` `5.0.0-rc.9`

Repository

Affected commits	Fixed by commit
GIT github.com/team-alembic/ash_authentication.git ↗
c5f589058e04239263f50a1430eb17ea6d5dd1a2 to before 728b8d28c1b5f465fa1116ef044a815300fc733d	`728b8d28c1b5f465fa1116ef044a815300fc733d`
Not specified	`64530644f9b37ebb76ca14aeb83a77597a0034b7`
Also listed as affected (165) `v4.13.7` `5.0.0-rc.9` `5.0.0-rc.8` `v5.0.0-rc.7` `v5.0.0-rc.6` `v5.0.0-rc.5` `v5.0.0-rc.4` `v5.0.0-rc.3` `v5.0.0-rc.2` `v5.0.0-rc.1` `v5.0.0-rc.0` `v4.13.6` `v4.13.5` `v4.13.4` `v4.13.3` `v4.13.2` `v4.13.1` `v4.13.0` `v4.12.0` `v4.11.0` `v4.10.0` `v4.9.9` `v4.9.8` `v4.9.7` `v4.9.6` `v4.9.5` `v4.9.4` `v4.9.3` `v4.9.2` `v4.9.1` `v4.9.0` `v4.8.7` `v4.8.5` `v4.8.4` `v4.8.3` `v4.8.2` `v4.8.1` `v4.8.0` `v4.7.7` `v4.7.6` `v4.7.5` `v4.7.4` `v4.7.3` `v4.7.2` `v4.7.1` `v4.7.0` `v4.6.4` `v4.6.3` `v4.6.2` `v4.6.1` `v4.6.0` `v4.5.6` `v4.5.5` `v4.5.4` `v4.5.3` `v4.5.2` `v4.5.1` `v4.4.9` `v4.4.8` `v4.4.7` `v4.4.6` `v4.4.5` `v4.4.4` `v4.4.3` `v4.4.2` `v4.4.1` `v4.4.0` `v4.3.12` `v4.3.10` `v4.3.9` `v4.3.7` `v4.3.6` `v4.3.4` `v4.3.3` `v4.3.2` `v4.3.1` `v4.3.0` `v4.2.7` `v4.2.5` `v4.2.3` `v4.2.2` `v4.2.1` `v4.2.0` `v4.1.0` `v4.0.4` `v4.0.3` `v4.0.2` `v4.0.1` `v4.0.0` `v4.0.0-rc.7` `v4.0.0-rc.6` `v4.0.0-rc.5` `v4.0.0-rc.4` `v4.0.0-rc.3` `v4.0.0-rc.2` `v4.0.0-rc.1` `v4.0.0-rc.0` `v3.12.4` `v3.12.3` `v3.12.2` `v3.12.1` `v3.12.0` `v3.11.16` `v3.11.15` `v3.11.14` `v3.11.13` `v3.11.12` `v3.11.10` `v3.11.9` `v3.11.8` `v3.11.7` `v3.11.6` `v3.11.5` `v3.11.4` `v3.11.3` `v3.11.2` `v3.11.1` `v3.11.0` `v3.10.8` `v3.10.7` `v3.10.6` `v3.10.5` `v3.10.4` `v3.10.2` `v3.10.1` `v3.10.0` `v3.9.6` `v3.9.5` `v3.9.4` `v3.9.3` `v3.9.2` `v3.9.0` `v3.7.9` `v3.7.8` `v3.7.6` `v3.7.5` `v3.7.4` `v3.7.3` `v3.7.2` `v3.7.1` `v3.7.0` `v3.6.1` `v3.5.3` `v3.5.2` `v3.5.1` `v3.5.0` `v3.4.2` `v3.4.1` `v3.4.0` `v3.3.1` `v3.3.0` `v3.2.2` `v3.2.1` `v3.2.0` `v3.1.0` `v3.0.4` `v3.0.3` `v3.0.2` `v3.0.1` `v3.0.0` `v2.0.1` `v2.0.0` `v1.0.0` `v0.6.1` `v0.6.0`

Description

Summary

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.