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High · 7.6 CVE-2026-80218 EEF-CVE-2026-80218EUVD-2026-81484GHSA-3pr8-f99q-86hp

Sign-in token minted for one resource accepted by another in AshAuthentication

Published Sep 17, 2026 · Updated Sep 17, 2026 · Assigned by EEF

Description

Improper Authentication vulnerability in team-alembic AshAuthentication allows an attacker holding a sign-in token for one authenticated resource to be signed in as a user of a different resource.

AshAuthentication.Strategy.Password.SignInWithTokenPreparation.extract_primary_keys_from_subject/2 parses the JWT sub claim (for example user?id=1) with URI.parse/1 and keeps only its query string, discarding the path segment that names the subject the token was issued for. Nothing else restores that binding: AshAuthentication.Jwt.verify/3 checks the signature, exp, nbf, jti and the library-version claims, the purpose check only requires sign_in, and the remaining comparison is over primary-key field names, which are identical across resources. The WebAuthn sign-in and remember-me preparations carry copies of the same helper and drop the path in the same way. The magic link sign-in path pins the subject name against the resource and is not affected.

This issue affects ash_authentication: from 3.10.5 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

Affected products

VendorProductAffectedFixed
team-alembic ash_authentication 3.10.5 – < 4.15.0, 5.0.0-rc.0 – < 5.0.0-rc.14 4.15.0

Affected packages

EcosystemPackageAffectedFixedRecord
Hex ash_authentication >= 3.10.5, < 4.15.0 · >= 5.0.0-rc.0, < 5.0.0-rc.14 4.15.0, 5.0.0-rc.14 EEF-CVE-2026-80218

References