---
id: CVE-2026-102408
title: >-
  Inefficient Regular Expression Complexity (CWE-1333) in Elasticsearch can lead
  to denial of service via Regular Expression Exponential Blowup (CAPEC-492)
summary: >-
  Inefficient Regular Expression Complexity (CWE-1333) in Elasticsearch can lead
  to denial of service via Regular Expression Exponential Blowup (CAPEC-492).
  The ES|QL CHUNK function's recursive chunking strategy accepts a list of
  user-supp…
severity: medium
cvss: 4.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-1333
vendor: Elastic
product: Elasticsearch
affected:
  - Elasticsearch >= 8.19.0 <= 8.19.21
  - Elasticsearch >= 9.1.0 <= 9.3.8
  - Elasticsearch >= 9.4.0 <= 9.4.7
  - Elasticsearch >= 9.5.0 <= 9.5.4
published: '2026-10-06'
updated: '2026-10-06'
sourceUpdated: '2026-10-06T20:17:12.777'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-102408'
references:
  - url: >-
      https://discuss.elastic.co/t/elasticsearch-8-19-22-9-4-8-and-9-5-5-security-update-esa-2026-189/390862
    label: security@elastic.co
tags:
  - nvd
  - cve.org
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-06T19:55:55.653697Z'
ingestedAt: '2026-10-06T20:16:42.473Z'
---

## Overview

Inefficient Regular Expression Complexity (CWE-1333) in Elasticsearch can lead to denial of service via Regular Expression Exponential Blowup (CAPEC-492). The ES|QL CHUNK function's recursive chunking strategy accepts a list of user-supplied regular expressions used as text-splitting separators, without validating their computational complexity or bounding their execution time. An authenticated user with read access to any text-based index can submit a specially crafted regular expression that triggers catastrophic backtracking, consuming excessive CPU on Elasticsearch worker threads and degrading query throughput for other tenants on the affected node. The cluster does not crash as a result of this issue.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.