Vulnerability · Published Oct 6, 2026 · Assigned by elastic
CVE-2026-102408Inefficient Regular Expression Complexity in Elasticsearch Leading to Denial of Service
Medium 4.3
In plain English
A medium-severity regular-expression denial of service in Elasticsearch from Elastic. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities).
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Elastic | Elasticsearch | 8.19.0 – through 8.19.219.1.0 – through 9.3.89.4.0 – through 9.4.79.5.0 – through 9.5.4 |
Weakness: CWE-1333 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L