Inefficient Regular Expression Complexity in Elasticsearch Leading to Denial of Service

Description

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.

Scores

EPSS (exploitation in 30 days)

0.35% · top 72% of all CVEs (4 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 4.3.

Weakness

• CWE-1333 Inefficient Regular Expression Complexity (opens in a new tab)All about CWE-1333 and its CVEs

Affected products

• Elastic · Elasticsearch

  • affected 8.19.0 – ≤ 8.19.21
  • affected 9.1.0 – ≤ 9.3.8
  • affected 9.4.0 – ≤ 9.4.7
  • affected 9.5.0 – ≤ 9.5.4

References (1)

• https://discuss.elastic.co/t/elasticsearch-8-19-22-9-4-8-and-9-5-5-security-update-esa-2026-189/390862 (opens in a new tab)

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-102408](https://trackcve.app/badge/CVE-2026-102408.svg)](https://trackcve.app/cve/CVE-2026-102408)

Record last updated 6 Oct 2026, 19:56 UTC.