CVE-2026-78699

Summary

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.

Affected Software

Weaknesses

• CWE-252: CWE-252 Unchecked Return Value

References

• https://github.com/ash-project/ash_postgres/security/advisories/GHSA-6fqq-j9c4-5766
• https://cna.erlef.org/cves/CVE-2026-78699.html
• https://osv.dev/vulnerability/EEF-CVE-2026-78699
• https://github.com/ash-project/ash_postgres/commit/8544ab15fe45784553c2d2da8ee1a388eee0174b

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