Apache Iceberg CVE-2026-42812 Bypasses Metadata Location Validation

Apache Iceberg is affected by CVE-2026-42812, a critical vulnerability in how its Polaris-managed catalogs handle metadata file locations. According to the National Vulnerability Database, an attacker with privileges to change table settings can manipulate the write.metadata.path property. This bypasses a crucial commit-time validation step that is supposed to revalidate storage locations for metadata files. The core issue is that Polaris skips intended location checks before performing security-sensitive metadata writes when only this property changes.

Under specific configurations, particularly when polaris.config.allow.unstructured.table.location is set to true and allowedLocations are broad, this flaw becomes exploitable. The National Vulnerability Database states that Polaris can be coerced into writing new table metadata to an attacker-controlled storage location. If this location is subsequently accepted by concrete-path validation, Polaris can then issue temporary cloud storage credentials for that same attacker-chosen area without revalidation. This means Polaris effectively hands out access to an attacker-designated storage location.

The implications are severe. The attacker-chosen storage area isn’t limited to the poisoned table’s own files; it could be a broader storage prefix, another table’s prefix, or even an entire bucket/container root, depending on the configuration. This could lead to widespread data and metadata exposure or corruption. Even if the credential vending step is prevented, Polaris itself performs the initial metadata write to an unchecked location, marking a significant security bypass.