CVE-2026-42812

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.