CVE-2026-78699 rename_tenant returns :ok on a failed rename, enabling cross-tenant access in AshPostgres
Attackers can rename tenants to collide with existing schemas, gaining unauthorized read and write access to other tenants' data due to unchecked return values.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-78699?
CVE-2026-78699 is a high-severity vulnerability in ash-project ash_postgres, published on 30 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Unchecked Return Value vulnerability in ash-project ash_postgres allows a user who can drive a tenant rename to a name that collides with an existing tenant's schema to have their tenant record repointed at that other tenant's live schema, gaining access to its data.
AshPostgres.MultiTenancy.rename_tenant/3 issues the ALTER SCHEMA ... RENAME TO ... with the non-raising Ecto.Adapters.SQL.query/2, discards its {:ok, _} | {:error, _} result, and unconditionally returns :ok. PostgreSQL rejects the rename when the target schema already exists (and on insufficient privilege or lock timeout), but that failure never reaches the caller. The calling manage_tenant update action therefore sees success and commits the tenant row with the new name, which is the schema of a different existing tenant, so subsequent reads and writes for that tenant run against the other tenant's data.
This issue affects ash_postgres: from 0.25.0 before 2.13.0.
Weakness: CWE-252
Which versions are affected by CVE-2026-78699?
1 open source package ship an affected version, including ash_postgres.
| Package | Affected | Fixed in |
|---|---|---|
ash_postgres Hex | From 0.25.0 | 2.13.0 |
How do I fix CVE-2026-78699?
Upgrade ash_postgres to 2.13.0 or later.
Is CVE-2026-78699 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-78699 exists.
Sources
Also known as EEF-CVE-2026-78699, GHSA-6fqq-j9c4-5766.