Cloudnative Pg

### Impact The CloudNativePG metrics exporter opens its PostgreSQL connection as the `postgres` superuser via the pod-local Unix socket, then demotes the session with `SET ROLE pg_monitor`. `SET ROLE` changes only `current_user`; `session_user` remains `postgres`. That residual superuser identity is the foothold for the rest of the chain. Any SQL expression evaluated inside the scrape session can invoke `RESET ROLE` to recover real superuser privileges, then use `COPY ... TO PROGRAM` to spawn an OS-level subprocess as the `postgres` user inside the primary pod. The `READ ONLY` transaction flag does not block this; it gates writes to database state, not external processes. Two exploitation paths follow from this root cause. #### Path 1: custom metric queries with unqualified identifiers (all supported releases) A database user who owns a schema on the `search_path` of any scraped database can plant a shadow object whose name matches an unqualified identifier in a custom metric query. When the exporter next evaluates that query, the shadow expression executes inside the `session_user = postgres` scrape session, giving the attacker PostgreSQL superuser privileges and OS command execution inside the primary pod within one scrape interval (≤30 s). Exploitability requires a custom metric query that contains an unqualified relation or function reference. Although `search_path` shadowing of unqualified identifiers is the most direct case, the underlying bug is that any expression evaluated inside the scrape session is a superuser code path. Other exploitable shapes include user-defined functions, operators or casts resolved during the scrape, joins or subqueries against user-owned tables and views, and index expressions or RLS policies on read-touched objects. #### Path 2: stock `default-monitoring.yaml` (all supported releases, no custom metrics required) The `pg_extensions` metric shipped in `default-monitoring.yaml` used an unqualified `current_database()` call and ran against every user database (`target_databases: '*'`). Any non-superuser who owns a user database (including the default `app` role created by `bootstrap.initdb`) could shadow `current_database()` and trigger the full escalation chain against a stock CNPG deployment on the first scrape after the shadow was planted. #### Combined impact The chain yields privilege escalation from a low-privileged database role (e.g. the default `app` role) to PostgreSQL superuser, plus arbitrary OS command execution as the `postgres` user inside the primary pod, all within one scrape interval. A web application SQL injection vulnerability in an app backed by a CNPG cluster is therefore sufficient to pivot to database-pod RCE. #### Who is impacted - All deployments on any supported release with default monitoring enabled are affected by Path 2. - All deployments on any supported release that use custom metric queries containing unqualified catalog references are affected by Path 1. - Multi-tenant platforms that allow customers to supply or influence custom metric query bodies are at the highest risk for Path 1. ### Patches Three separate patches address the vulnerability. #### Patch 1: PR #10576 "schema-qualify catalog references in default monitoring queries and documentation samples" Schema-qualifies all unqualified `pg_catalog` function and view references in the shipped `default-monitoring.yaml` and in documentation examples. This closes Path 2 in operator-shipped configuration and removes the unqualified-identifier attack surface from all operator-shipped metric queries. Operators who clone or copy `default-monitoring.yaml` into custom monitoring `ConfigMap`s, or have copy-pasted unqualified queries elsewhere, must re-qualify those queries themselves. Backported to all currently supported releases: - **v1.29.x** (x ≥ 1) - **v1.28.x** (x ≥ 3) #### Patch 2: "dedicated `cnpg_metrics_exporter` role with `pg_ident.conf` peer mapping" Introduces a dedicated `cnpg_metrics_exporter` PostgreSQL role (granted `pg_monitor`, no superuser privileges) and maps it in `pg_ident.conf` via peer authentication on the local Unix socket, following the same pattern already used for `cnpg_pooler_pgbouncer`. The metrics exporter connects as this role instead of `postgres`, so `session_user` is never a superuser and `RESET ROLE` has no escalation effect. This eliminates the root cause entirely. Demoting the session at the SQL level (via `SET SESSION AUTHORIZATION pg_monitor`) is not sufficient: the privilege check for `SET SESSION AUTHORIZATION` is whether the *authenticated* user is a superuser, not the current `session_user`. With the connection still authenticated as `postgres`, any SQL in the session can run `RESET SESSION AUTHORIZATION` and recover the original superuser identity. This is the same recovery primitive as `RESET ROLE`, one layer up. Only changing the authenticated user closes the loop. With this change in place, the original chain breaks at every step: `RESET ROLE` and `RESET SESSION AUTHORIZATION` cannot recover superuser, and `COPY ... TO PROGRAM` requires a privilege `pg_monitor` does not grant. As defense in depth, the monitoring transaction also prepends `pg_catalog` to the connection's `search_path`, so unqualified catalog identifiers cannot resolve to user-planted shadow objects. This patch changes the connection identity but not how queries are evaluated. Custom metric queries within `pg_monitor`'s scope (catalog reads, `pg_stat_*` views, settings) continue to work without modification. Queries that previously relied on superuser-level access (reading user-owned tables not granted to `cnpg_metrics_exporter`, or superuser-only catalogs such as `pg_authid` or `pg_subscription`) will fail and need explicit `GRANT` statements to `cnpg_metrics_exporter`. The role is created and maintained with `PASSWORD NULL`; any password set out-of-band is cleared on the next reconcile, so the role cannot be authenticated by password regardless of operator pre-creation. For replica clusters, upgrade the source primary cluster before any replica clusters that consume from it. The `cnpg_metrics_exporter` role is created on the source primary and replicates downstream; a replica cluster upgraded first will scrape against a missing role until the source primary upgrades or the role is created manually (see the monitoring documentation). The patch will be backported to all currently supported releases: - **v1.29.x** (x ≥ 1) - **v1.28.x** (x ≥ 3) ### Workarounds If upgrading immediately is not possible: 1. **Schema-qualify all identifiers in custom metric queries.** Use explicit `pg_catalog.` prefixes for all catalog functions and views (e.g. `pg_catalog.current_database()`, `pg_catalog.now()`). This is a partial mitigation: it closes the `search_path`-shadowing shape in operator- and user-supplied metric bodies, but other expression shapes (user-defined functions, operators or casts; joins or subqueries on user-owned tables and views; RLS policies on read-touched objects) remain superuser code paths until Patch 2 lands. 2. **Restrict database ownership.** Ensure only fully trusted roles own user databases in scraped clusters. The exploit requires the ability to plant an object on the metrics exporter's `search_path` in a scraped database, typically by owning the database (and therefore `public` via `pg_database_owner`) or by holding `CREATE` on a schema already reachable through `search_path`. *PG <15 caveat:* `public` grants `CREATE` to `PUBLIC` by default before PostgreSQL 15, so any authenticated role in a scraped database can plant a shadow object regardless of ownership. 3. **Limit the scope of `target_databases: '*'` queries.** Avoid `target_databases: '*'` unless every database in the cluster, and every role that owns one, is fully trusted. Where possible, restrict `target_databases` to specific, known-safe databases. 4. **Do not expose metric query SQL to untrusted users.** Multi-tenant platforms that allow customers to supply or influence custom metric query bodies should treat this as a critical trust boundary until the architectural fix is released. ### References - Fix (Patch 1): PR #10576 "schema-qualify catalog references in default monitoring queries and documentation samples" - Fix (Patch 2): "dedicated `cnpg_metrics_exporter` role with `pg_ident.conf` peer mapping" - Reported by: Mehmet Ince