Vulnerability in Elasticsearch

[ Description ]Official 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.

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• CERT-FR7 Oct 2026CERTFR-2026-AVI-1276

  Multiple vulnerabilities in Elastic products Translated from French

  Multiple vulnerabilities have been discovered in Elastic products. Some of them allow an attacker to cause privilege escalation, a breach of data confidentiality and a security policy bypass.

  CVE-2026-102406CVE-2026-103006CVE-2026-102404+11 more CVEs
• BSI CERT-Bund6 Oct 2026WID-SEC-2026-3784

  Elasticsearch: Multiple vulnerabilities Translated from German

  CVE-2026-102404CVE-2026-103005CVE-2026-103006+7 more CVEs

[ References ]References

• discuss.elastic.co/t/elasticsearch-8-19-22-9-4-8-and-9-5-5-security-update-esa-2026-189…Vendor Advisory