CVE-2026-102408: Inefficient Regular Expression Complexity in Elasticsearch Leading to Denial of Service
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 Software
Event History
Frequently Asked Questions
Who can exploit this issue?
An authenticated user with read access to any text-based index can submit the crafted query. The impact is most relevant where such users can run ES|QL queries using the CHUNK function.
What does an attacker need to do to trigger the denial of service?
The attacker must supply a specially crafted regular expression in the user-provided list of text-splitting separators accepted by the ES|QL CHUNK function. The expression triggers catastrophic backtracking during recursive chunking and consumes Elasticsearch worker-thread CPU.
What is the expected operational impact?
Exploitation can degrade query throughput for other tenants on the affected node by exhausting CPU on worker threads. The provided information states that the cluster does not crash.