CVE-2026-78223

01/Description

Improper Verification of Cryptographic Signature vulnerability in team-alembic AshAuthentication allows a caller of the token revocation action to neutralise a revocation or write arbitrary rows into the token resource. AshAuthentication.TokenResource.RevokeTokenChange.change/3 reads the :token argument and decodes it with AshAuthentication.Jwt.peek/1, which delegates to Joken.peek_claims/1 and performs no signature check, unlike Jwt.verify/4. The jti, exp and sub claims it returns are written straight onto the revocation record, guarded only by byte_size(token) > 0. Because expires_at derives from the attacker-chosen exp, a forged copy of a genuine token that keeps the real jti but backdates exp yields a revocation row that is already expired: expunge_expired removes it and the genuine token passes revoked? again. Arbitrary jti and sub values can be inserted the same way. This issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.

02/References6

• cna.erlef.org/cves/CVE-2026-78223.html
• github.com/team-alembic/ash_authentication/commit/344cebb12faf6…
• github.com/team-alembic/ash_authentication/commit/a939dde9b917c…
• github.com/team-alembic/ash_authentication/commit/eb86353fe5a54…
• github.com/team-alembic/ash_authentication/security/advisories/…
• osv.dev/vulnerability/EEF-CVE-2026-78223