CVE-2026-56144: Elasticsearch Auth Bypass Vulnerability

CVE-2026-56144 Overview

CVE-2026-56144 is an Incorrect Authorization vulnerability [CWE-863] in Elasticsearch that affects the ingest simulation feature. An authenticated user with limited index privileges can bypass authorization controls to trigger ingest pipelines on indices they cannot access directly. The feature returns the pipeline output, potentially disclosing data processed or enriched by those pipelines. The same feature also enables retrieval of index mapping metadata for restricted indices. Elastic addressed the issue in Elasticsearch versions 8.19.18, 9.3.7, and 9.4.4 as documented in the ESA-2026-56 advisory.

Critical Impact
Authenticated users with limited privileges can disclose data from indices they are not authorized to read, including pipeline-processed content and index mapping metadata.

Affected Products

Elasticsearch 8.x prior to 8.19.18
Elasticsearch 9.3.x prior to 9.3.7
Elasticsearch 9.4.x prior to 9.4.4

Discovery Timeline

2026-07-21 - CVE-2026-56144 published to NVD
2026-07-22 - Last updated in NVD database

Technical Details for CVE-2026-56144

Vulnerability Analysis

Elasticsearch supports ingest pipelines that process documents at index time. The ingest simulation API lets clients test how documents would be transformed by a pipeline before actual ingestion. The vulnerability stems from insufficient authorization checks when the simulation API references indices the caller cannot access directly. The API executes the target index's configured ingest pipelines and returns the transformed output. This exposes enriched or processed data derived from restricted indices. The same code path leaks index mapping metadata associated with those indices.

Root Cause

The ingest simulation feature validates the caller's identity but fails to enforce full authorization against the referenced index. The check treats simulation as a lower-privilege action than direct index access. This assumption is incorrect because pipelines can transform sensitive source data and return it to the caller. Mapping metadata retrieval follows the same flawed authorization path.

Attack Vector

The attacker must hold valid Elasticsearch credentials with limited index privileges. From an authenticated session, the attacker issues an ingest simulation request that names a restricted target index. Elasticsearch resolves the index's configured pipelines, executes them, and returns pipeline output plus mapping metadata. No user interaction is required. Attack complexity is high because the attacker must know or discover the target index name and pipeline configuration. See the Elastic Security Update ESA-2026-56 for authoritative technical details.

Detection Methods for CVE-2026-56144

Indicators of Compromise

Unexpected POST requests to /_ingest/pipeline/_simulate or /_ingest/pipeline/{id}/_simulate from accounts with limited privileges.
Simulation requests that reference index names outside the caller's normal access scope.
Elevated volumes of ingest simulation calls from a single API key or service account.

Detection Strategies

Enable Elasticsearch audit logging and correlate authentication_success events with _simulate endpoint access.
Baseline legitimate ingest simulation usage per role, then alert on deviations from the baseline.
Compare accessed index names in simulation payloads to the caller's role mapping to detect privilege boundary crossings.

Monitoring Recommendations

Forward Elasticsearch audit logs to a centralized analytics platform for retention and correlation.
Alert on simulation requests targeting indices tagged as sensitive, such as those containing personally identifiable information or credentials.
Review API key usage regularly and rotate keys that show anomalous simulation activity.

How to Mitigate CVE-2026-56144

Immediate Actions Required

Upgrade Elasticsearch to 8.19.18, 9.3.7, 9.4.4, or later as directed by Elastic.
Audit all roles that grant any index privileges and remove unnecessary access to sensitive indices.
Review ingest pipelines that enrich data with sensitive fields and evaluate exposure risk.

Patch Information

Elastic released fixed versions 8.19.18, 9.3.7, and 9.4.4. Refer to the Elastic Security Update ESA-2026-56 for the full advisory, affected versions, and upgrade guidance.

Workarounds

Restrict access to the ingest simulation API by removing broad cluster or index privileges from low-trust roles until patching completes.
Isolate sensitive indices onto dedicated clusters with strict role-based access control, limiting who can call simulation endpoints.
Enable and monitor audit logs so that any exploitation attempt is recorded for investigation.

bash

# Configuration example: restrictive role that omits ingest simulation privileges
POST /_security/role/limited_reader
{
  "cluster": [],
  "indices": [
    {
      "names": ["public-*"],
      "privileges": ["read"]
    }
  ]
}