CVE-2026-42811
Published: 04 May 2026
Summary
CVE-2026-42811 is a critical-severity Improper Input Validation (CWE-20) vulnerability in Apache Polaris. Its CVSS base score is 9.9 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 29.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and SI-2 (Flaw Remediation).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Requires validation of namespace and table identifiers to prevent crafted inputs from breaking out of CEL quoted strings and broadening GCS credential scope.
Mandates timely remediation of the Polaris flaw through patching to fix improper escaping in CEL expression construction.
Enforces proper access control mechanisms to ensure delegated GCS credentials adhere to intended table-specific path restrictions.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vuln in network-accessible Polaris catalog service (AV:N) is directly exploitable via T1190 to bypass CAB/CEL policy restrictions, enabling T1068 for scope escalation to overprivileged GCS tokens; resulting access directly facilitates T1530 (read/list metadata/objects), T1565.001 (create/modify objects under other prefixes), and T1485 (delete objects).
NVD Description
In plain terms, Apache Polaris is supposed to issue short-lived GCS credentials that only work for one table's files, but a crafted namespace or table name can cause those credentials to work across the configured bucket instead. Apache Polaris builds…
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Google Cloud Storage downscoped credentials by creating a Credential Access Boundary (CAB) with CEL conditions that are intended to restrict access to the requested table's storage path. The relevant CEL string is built from the bucket name and the table path. That table path is derived from namespace and table identifiers. In current code, that path appears to be inserted into the CEL expression without escaping. As a result, a namespace or table identifier containing a single quote and other URI-safe CEL fragments can break out of the intended quoted string and change the meaning of the CEL condition. In private testing against Polaris 1.4.0 on real Google Cloud Storage, it was confirmed that Polaris accepted a crafted identifier and returned delegated GCS credentials whose CEL path restriction had effectively collapsed. Those delegated credentials could then: - list another table's object prefix; - read another table's metadata control file (Iceberg metadata JSON); - create and delete an object under another table's object prefix; - and also list, read, create, and delete objects under an unrelated external prefix in the same bucket that was not part of any table path. That last point is important. The issue is not limited to "another table". In the confirmed setup, once Apache Polaris returned credentials for the crafted table, the path restriction inside the configured bucket was effectively gone. The practical effect is that temporary credentials for one crafted table can be broader than the table Polaris was asked to authorize, and can become effectively bucket-wide within the configured bucket. The current GCS testing used a Polaris principal with broad catalog privileges for setup. A separate least-privilege Polaris RBAC variant has not yet been tested on GCS. However, the storage-credential broadening behavior itself has been confirmed on GCS.
Deeper analysisAI
Apache Polaris, an open-source catalog for Apache Iceberg tables, contains a vulnerability (CVE-2026-42811) in its generation of short-lived Google Cloud Storage (GCS) credentials. Polaris constructs Credential Access Boundary (CAB) policies using CEL conditions to restrict access to a specific table's storage path, derived from namespace and table identifiers. Due to improper escaping, a crafted namespace or table name containing a single quote and URI-safe CEL fragments can break out of the quoted string in the CEL expression, altering the condition to effectively remove path restrictions within the configured GCS bucket. This issue was confirmed in private testing against Polaris 1.4.0 using real GCS infrastructure.
An authenticated attacker with low privileges (PR:L), such as a Polaris principal with catalog privileges, can exploit this by requesting credentials for a crafted table or namespace. The resulting delegated GCS credentials grant broader-than-intended access across the bucket, enabling the attacker to list object prefixes of other tables, read their Iceberg metadata JSON files, create and delete objects under other tables' prefixes, and perform list, read, create, and delete operations on unrelated prefixes in the same bucket. The CVSS v3.1 score of 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H) reflects the network-accessible, low-complexity exploitation leading to high confidentiality, integrity, and availability impacts. Testing used a principal with broad catalog privileges; least-privilege RBAC variants remain untested for this storage credential broadening.
Advisories detailing the issue appear on the Apache mailing lists (https://lists.apache.org/thread/hovn5hmkj9wj7v9cd8sn67svg03klgvg) and OSS-Security (http://www.openwall.com/lists/oss-security/2026/05/02/12), published around May 4, 2026. No specific patch or mitigation details are provided in the available information.
Details
- CWE(s)