Quick answers
- Is CVE-2026-102408 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-102408 being exploited in the wild.
- How severe is CVE-2026-102408?
- Medium severity, with a CVSS score of 4.3, published 6 October 2026.
- Which products and versions are affected?
- Elasticsearch 8.19.0–8.19.21; 9.1.0–9.3.8; 9.4.0–9.4.7; 9.5.0–9.5.4.
- Is there a fix for CVE-2026-102408?
- Yes: fixed in Elasticsearch 8.19.22, 9.4.8, 9.5.5. Until then: No workarounds are available. Users unable to upgrade immediately should restrict ES|QL query access and review deployment access controls to limit who can issue CHUNK function queries. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-102408 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-102408?
- Check whether you run Elasticsearch at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Elasticsearch 8.19.22, 9.4.8, 9.5.5
No workarounds are available. Users unable to upgrade immediately should restrict ES|QL query access and review deployment access controls to limit who can issue CHUNK function queries.
Technical details
The ES|QL CHUNK function's recursive chunking strategy does not validate the computational complexity of user-supplied regular expressions used as text-splitting separators, enabling catastrophic backtracking attacks. Any authenticated user with read access to a text-family index can exploit this via network queries. The vulnerability causes denial of service through CPU exhaustion on worker threads, without cluster-wide impact; a fix exists in patched versions.
Affected products
- Elastic Elasticsearch 8.19.0–8.19.21; 9.1.0–9.3.8; 9.4.0–9.4.7; 9.5.0–9.5.4
Timeline
- 2026-10-06: disclosed