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CVE-2026-102408

Inefficient Regular Expression Complexity in Elasticsearch Leading to Denial of Service

Elastic ElasticsearchDatabases
Open in ThreatlineRecord JSON
CVSS
4.3Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.35%Chance of exploitation activity in the next 30 days, higher than 27% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published6 Oct 2026Updated 6 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

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.

Text from CVE List

Affected versions 4

  • Elasticsearchaffected: 8.19.0 through 8.19.21CVE List
  • Elasticsearchaffected: 9.1.0 through 9.3.8CVE List
  • Elasticsearchaffected: 9.4.0 through 9.4.7CVE List
  • Elasticsearchaffected: 9.5.0 through 9.5.4CVE List

References 1