Elasticsearch 9.0.x < 9.4.8 / 9.5.x < 9.5.5 Incorrect Authorization (ESA-2026-199)

high Nessus Plugin ID 363430

Synopsis

The remote host is missing a security update.

Description

The version of Elasticsearch installed on the remote host is 9.0.x prior to 9.4.8, or 9.5.x prior to 9.5.5. It is, therefore, affected by a vulnerability as referenced in the ESA-2026-199 advisory.

- Authorization Bypass Through User-Controlled Key (CWE-639) in Elasticsearch can lead to Information Disclosure via a specially crafted cross-cluster search request that references an unauthorized shard identifier. Elasticsearch contains an authorization bypass weakness in its handling of cross-cluster search requests made through the Remote Cluster Security (RCS) 2.0 model. An authorization check validates a request against one identifying attribute of the target shard, while a separate, independently-supplied identifying attribute in the same request determines which shard is actually accessed. A holder of a cross-cluster API key authorized for one index can craft a request whose two identifying attributes refer to different indices, causing the request to be authorized against an index they can access while actually operating against a different, unauthorized index. This can expose that index's document contents, field mappings, and other metadata, and in limited cases allows modification of retention-lease state on the unauthorized index. (CVE-2026-103009)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Elasticsearch version 9.4.8, or 9.5.5 or later as appropriate for your release branch.

Plugin Details

Severity: High

ID: 363430

File Name: elasticsearch_esa_2026_199.nasl

Version: 1.1

Type: Combined

Agent: unix

Family: Misc.

Published: 10/6/2026

Updated: 10/6/2026

Configuration: Enable thorough checks (optional)

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Low

Score: 3.5

Percentile: 51.48

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:P/A:N

CVSS Score Source: CVE-2026-103009

CVSS v3

Risk Factor: High

Base Score: 7.1

Temporal Score: 6.2

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:elastic:elasticsearch, cpe:/a:elasticsearch:elasticsearch

Required KB Items: installed_sw/Elasticsearch

Exploit Ease: No known exploits are available

Patch Publication Date: 10/6/2026

Vulnerability Publication Date: 10/6/2026

Reference Information

CVE: CVE-2026-103009

Detections

Analytics