CVE-2026-80218 Sign-in token minted for one resource accepted by another in AshAuthentication
Attackers can use a sign-in token from one resource to authenticate as a user on a different resource due to improper JWT subject validation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80218?
CVE-2026-80218 is a high-severity authentication bypass vulnerability in team-alembic ash_authentication, published on 17 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official 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.
Weakness: CWE-287
Which versions are affected by CVE-2026-80218?
1 open source package ship an affected version, including ash_authentication.
| Package | Affected | Fixed in |
|---|---|---|
ash_authentication Hex | From 3.10.5 | 4.15.0, 5.0.0-rc.14 |
How do I fix CVE-2026-80218?
Upgrade ash_authentication to a fixed version for your release line: 4.15.0 or 5.0.0-rc.14.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-80218 being exploited?
There is no known exploitation of CVE-2026-80218 in the wild and no public exploit code.
Sources
Also known as EEF-CVE-2026-80218, GHSA-3pr8-f99q-86hp.