OAuth2/OIDC account takeover in AshAuthentication via email-based user matching
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-49757
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 13:16 UTC · Revision 1
Source evidence
OAuth2/OIDC account takeover in AshAuthentication via email-based user matching
core-osv · Original sourcePublished 15 Jun 2026, 10:07 UTC
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.
osv:CVE-2026-49757
Complete source record
{
"id": "60c64e49ec537ff9249de85e41286f7823b2e5f39966a9ef4d62e05e49e31b9f",
"url": "https://osv.dev/vulnerability/CVE-2026-49757",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "OAuth2/OIDC account takeover in AshAuthentication via email-based user matching",
"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.",
"evidence": "osv:CVE-2026-49757",
"products": [],
"severity": "critical",
"structured": {
"id": "CVE-2026-49757",
"aliases": [
"CVE-2026-49757",
"EEF-CVE-2026-49757",
"GHSA-777c-2fxx-qr28"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS: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": [
{
"ranges": [
{
"repo": "https://github.com/team-alembic/ash_authentication",
"type": "GIT",
"events": [
{
"introduced": "c5f589058e04239263f50a1430eb17ea6d5dd1a2"
},
{
"fixed": "728b8d28c1b5f465fa1116ef044a815300fc733d"
},
{
"introduced": "641ae5d2cb95ba191b9efbc59dcea61f0a570a95"
},
{
"fixed": "8badd8f3d618fb864bda1b041c815f7925c35861"
},
{
"introduced": "6767fe27eb952e5bc09aa2e5a7d8f96f5a1c424a"
},
{
"fixed": "8fa0d9823fbef04aaab517e7ea0f4b17976f1502"
},
{
"fixed": "64530644f9b37ebb76ca14aeb83a77597a0034b7"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
{
"introduced": "c5f589058e04239263f50a1430eb17ea6d5dd1a2"
},
{
"fixed": "728b8d28c1b5f465fa1116ef044a815300fc733d"
}
],
"source": "AFFECTED_FIELD",
"strategy": "ChangesAt"
},
{
"range": [
{
"introduced": "0.1.0"
},
{
"fixed": "4.14.0"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
},
{
"range": [
{
"introduced": "5.0.0-rc.0"
},
{
"fixed": "5.0.0-rc.10"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StandardRange"
},
{
"range": [
{
"fixed": "728b8d28c1b5f465fa1116ef044a815300fc733d"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "64530644f9b37ebb76ca14aeb83a77597a0034b7"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"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"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-49757.json"
}
}
],
"modified": "2026-10-28T02:30:35.399899978Z",
"provider": "osv",
"references": [
"https://cna.erlef.org/cves/CVE-2026-49757.html",
"https://github.com",
"https://osv.dev/vulnerability/EEF-CVE-2026-49757",
"https://repo.hex.pm",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49757.json",
"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-777c-2fxx-qr28",
"https://nvd.nist.gov/vuln/detail/CVE-2026-49757",
"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",
"https://github.com/team-alembic/ash_authentication.git"
],
"provider_metadata": {
"cwe_ids": [
"CWE-290"
],
"cna_assigner": "EEF",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49757.json"
}
},
"related_cves": [
{
"value": "CVE-2026-49757",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 502941,
"published_at": "2026-06-15T10:07:17.781+00:00"
}