CVE-2026-42812 Apache Polaris: No protection on `write.metadata.path`
Attackers can bypass storage location validation to write metadata to arbitrary locations, potentially exposing or corrupting data via credential vending.
- 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-2026-42812?
CVE-2026-42812 is a critical missing authorization vulnerability in Apache Polaris, published on 4 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In Apache Iceberg, the table's metadata files are control files: they tell readers which data files belong to the table and which table version to read.
`write.metadata.path` is an optional table property that tells Polaris where to write those metadata files. For a table already registered in a Polaris-managed catalog, changing only that property through an `ALTER TABLE`-style settings change (not a row-level `INSERT`, `SELECT`, `UPDATE`, or `DELETE`) bypasses the commit-time branch that is supposed to revalidate storage locations.
The full persisted / credential-vending variant requires the affected catalog to have `polaris.config.allow.unstructured.table.location=true`, with `allowedLocations` broad enough to include the attacker-chosen target.
`allowedLocations` is the admin-configured allowlist of storage paths that the catalog is allowed to use. Public project materials suggest that this flag is a real supported compatibility / layout mode, not just a contrived lab-only prerequisite.
In that configuration, a user who can change table settings can cause Apache Polaris itself to write new table metadata to an attacker-chosen reachable storage location before the intended location-validation branch runs.
If the later concrete-path validation also accepts that location, Polaris persists the resulting metadata path into stored table state. Later table-load and credential APIs can then return temporary cloud-storage credentials for the same location without revalidating it. In plain terms, Polaris can later hand out temporary storage access for the same attacker-chosen area.
That attacker-chosen area does not need to be limited to the poisoned table's own files. If it is a broader storage prefix, another table's prefix, or, depending on configuration or provider behavior, even a bucket/container root, the resulting disclosure or corruption scope can extend to any data and metadata Polaris can reach there.
The practical consequences are therefore similar to the staged-create credential-vending issue already discussed: data and metadata reachable in that storage scope can be exposed and, if write-capable credentials are later issued, modified, corrupted, or removed. Even before that later credential step, Polaris itself performs the metadata write to the unchecked location.
So the core issue is not only later credential vending.
The primary defect is that Polaris skips its intended location checks before performing a security- sensitive metadata write when only `write.metadata.path` changes.
When `polaris.config.allow.unstructured.table.location=false`, current code review suggests the later `updateTableLike(...)` validation usually rejects out-of-tree metadata locations before the unsafe path is persisted. That may reduce the persisted / credential-vending variant, but it does not prevent the underlying defect: Polaris still skips the intended pre-write location check when only `write.metadata.path` changes.
Which versions are affected by CVE-2026-42812?
2 open source packages ship an affected version, including org.apache.polaris:polaris-runtime-service. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
org.apache.polaris:polaris-runtime-service Maven | From 0.9.0 | 1.4.1 |
org.apache.polaris:polaris-runtime-service Maven | From 0.9.0 | 1.4.1 |
Products include Apache Polaris.
How do I fix CVE-2026-42812?
Upgrade org.apache.polaris:polaris-runtime-service to 1.4.1 or later.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-42812 being exploited?
There is no known exploitation of CVE-2026-42812 in the wild and no public exploit code.
Other vulnerabilities in Apache Polaris
- CVE-2026-42809 Apache Polaris: staged table creation could vend storage credentials for unvalidated locations
- CVE-2026-42810 Apache Polaris: could broaden vended S3 credentials through wildcard-bearing namespace or table names
- CVE-2026-42811 Apache Polaris has an Improper Input Validation issue
- CVE-2026-64640 Apache Polaris: register endpoint reads attacker-controlled storage location before allowed-locations validation
Sources
Also known as GHSA-w76p-3cgp-qfcm.