CVE-2026-42812: Apache Polaris has an Improper Input Validation issue

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.6%, percentile 47: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 47% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes org.apache.polaris:polaris-runtime-service (Maven) >= 0.9.0, < 1.4.1, fixed in 1.4.1. Check your lockfile, including transitive dependencies.

What it is

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…

From the GitHub advisory

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.

Weakness type: CWE-863, CWE-284, CWE-20, CWE-732.

Product: org.apache.polaris:polaris-runtime-service (Maven) · Assigned by: apache · Published: 2026-05-04

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: low (any account)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.59% probability of exploitation activity in the next 30 days; percentile 47.

Timeline

• 2026-05-04 — CVE record last updated
• 2026-05-04 — CVE record published by apache
• 2026-05-04 — GitHub-reviewed advisory GHSA-w76p-3cgp-qfcm published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. lists.apache.org lists.apache.org

Vulnerability records

1. GitHub Advisory GHSA-w76p-3cgp-qfcm github.com
2. CVE.org record CVE-2026-42812 cve.org
3. NVD entry CVE-2026-42812 nvd.nist.gov

Other references from the CVE record and advisory

1. openwall.com openwall.com
2. github.com github.com
3. github.com github.com

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