CVE-2026-42811: CWE-917 Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') in Apache Software Foundation Apache Polaris
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 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.
AI Analysis
Technical Summary
Apache Polaris issues short-lived GCS credentials scoped to a single table's files using Credential Access Boundary (CAB) with CEL conditions. The vulnerability stems from improper neutralization of special elements in the CEL expression, specifically unescaped single quotes and URI-safe fragments in namespace or table identifiers. This allows crafted identifiers to break out of the intended string context, altering the CEL condition to remove path restrictions. Testing on Polaris 1.4.0 confirmed that such crafted identifiers yield delegated credentials with access that extends across the entire configured bucket, not limited to the requested table path. This broadening of credential scope compromises the intended access control model and can lead to unauthorized data access and modification within the bucket.
Potential Impact
The vulnerability enables an attacker to obtain delegated GCS credentials with broader access than authorized, effectively removing path restrictions within the configured bucket. This can lead to unauthorized listing, reading, creation, and deletion of objects across multiple tables and unrelated prefixes within the bucket. The impact includes potential data exposure, data integrity compromise, and unauthorized data manipulation. The CVSS 4.0 score of 9.4 reflects critical severity with network attack vector, low attack complexity, no user interaction, and high impacts on confidentiality, integrity, availability, and security requirements.
Mitigation Recommendations
A patch is available for this vulnerability. Since Apache Polaris is a cloud service, the vendor typically manages remediation server-side. Users should consult the official Apache Polaris vendor advisory for confirmation of patch deployment and any additional mitigation steps. Until patched, avoid using untrusted or unvalidated namespace and table identifiers that could exploit this injection flaw. Monitor vendor communications for updates on the fix status and apply official patches promptly.
CVE-2026-42811: CWE-917 Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection') in Apache Software Foundation Apache Polaris
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 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.
CVSS v4.0
Score 9.4critical
Affected software
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Apache Polaris issues short-lived GCS credentials scoped to a single table's files using Credential Access Boundary (CAB) with CEL conditions. The vulnerability stems from improper neutralization of special elements in the CEL expression, specifically unescaped single quotes and URI-safe fragments in namespace or table identifiers. This allows crafted identifiers to break out of the intended string context, altering the CEL condition to remove path restrictions. Testing on Polaris 1.4.0 confirmed that such crafted identifiers yield delegated credentials with access that extends across the entire configured bucket, not limited to the requested table path. This broadening of credential scope compromises the intended access control model and can lead to unauthorized data access and modification within the bucket.
Potential Impact
The vulnerability enables an attacker to obtain delegated GCS credentials with broader access than authorized, effectively removing path restrictions within the configured bucket. This can lead to unauthorized listing, reading, creation, and deletion of objects across multiple tables and unrelated prefixes within the bucket. The impact includes potential data exposure, data integrity compromise, and unauthorized data manipulation. The CVSS 4.0 score of 9.4 reflects critical severity with network attack vector, low attack complexity, no user interaction, and high impacts on confidentiality, integrity, availability, and security requirements.
Mitigation Recommendations
A patch is available for this vulnerability. Since Apache Polaris is a cloud service, the vendor typically manages remediation server-side. Users should consult the official Apache Polaris vendor advisory for confirmation of patch deployment and any additional mitigation steps. Until patched, avoid using untrusted or unvalidated namespace and table identifiers that could exploit this injection flaw. Monitor vendor communications for updates on the fix status and apply official patches promptly.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- apache
- Date Reserved
- 2026-04-30T14:30:15.047Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
- Is Cloud Service
- true
Threat ID: 69f8d219cbff5d86103970ba
Added to database: 5/4/2026, 5:06:33 PM
Last enriched: 5/4/2026, 5:21:20 PM
Last updated: 6/18/2026, 9:09:49 PM
Views: 96
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