EEF-CVE-2026-78223 CVE-2026-78223 GHSA-mfwg-5cpf-px58

Token revocation record built from unverified JWT claims in AshAuthentication

Not rated yet Hex

Severity: 0.0 / 10; Unknown · CVSS 4.0
Exploit chance (EPSS): 0.44%; Chance of exploitation in the next 30 days. Higher than 38.39% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-347 Improper Verification of Cryptographic Signature
Fix: 5.0.0-rc.14; Upgrade ash_authentication to this version or later

Description

Summary

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.

Affected versions

Hex

Package	Vulnerable	Fixed in
ash_authentication	`>= 0.2.0, < 4.15.0` `>= 5.0.0-rc.0, < 5.0.0-rc.14`	`4.15.0` `5.0.0-rc.14`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

ash_authentication Hex → `5.0.0-rc.14`

mix

{:ash_authentication, "~> 5.0.0-rc.14"} # then: mix deps.update ash_authentication

Severity breakdown

CVSS 4.0 0.0

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

Attack vector: Network
Attack complexity: Low
Attack requirements: None
Privileges required: None
User interaction: None
Confidentiality (vulnerable system): None
Integrity (vulnerable system): Low
Availability (vulnerable system): None
Confidentiality (subsequent systems): None
Integrity (subsequent systems): None
Availability (subsequent systems): None

Weakness

CWE-347: Improper Verification of Cryptographic Signature

The product does not verify, or incorrectly verifies, the cryptographic signature for data.

References

Advisories

github.com/team-alembic/ash_authentication/security/advisories/GHSA-mfwg-5cpf-px58

Fixes and patches

Packages

hex.pm/packages/ash_authentication

Timeline

Sep 17, 2026 Published
Sep 18, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
EEF-CVE-2026-86688 Session id is not renewed on authentication in ash_authentication, allowing session fixation	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-76949 Remember-me sign-in guard reads a session key that is never written in ash_authentication, allowing session replacement	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-91039 dynamic_oidc identities are not namespaced by connection in ash_authentication, allowing cross-connection account takeover	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-88952 OAuth2 sign-in attached to an existing account without an email comparison in AshAuthentication	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-85500 `require_confirmed_with` is not enforced on the action and fails open on an unreadable attribute in AshAuthentication	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-86533 Revoked session accepted because the session jti is never checked in AshAuthentication and AshAuthentication Phoenix	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-81632 Single-use sign-in token placed in a redirect query string in AshAuthenticationPhoenix	Not rated yet	Also affects ash_authentication
EEF-CVE-2026-80218 Sign-in token minted for one resource accepted by another in AshAuthentication	Not rated yet	Also affects ash_authentication

Credits: James Harton, Jonatan Männchen / EEF, Peter Ullrich

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