What’s Vulnerable › Vulnerabilities
CVE-2026-102408: Inefficient Regular Expression Complexity in Elasticsearch Leading to Denial of Service
- Severity: medium (CVSS 4.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-10-06 · updated 2026-10-13
- Weakness: CWE-1333
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
- Elasticsearch: from 8.19.0 before 8.19.22; from 9.1.0 before 9.4.8; from 9.5.0 before 9.5.5 — fixed in 8.19.22, 9.4.8, 9.5.5
How to fix
Upgrade to a fixed version: Elasticsearch 8.19.22, 9.4.8, 9.5.5. Check the vendor advisory for mitigations.
References
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