Memory Allocation with Excessive Size Value in Elasticsearch Leading to Denial of Service
A flaw in Elasticsearch allows a low-privileged authenticated user to submit a single small request containing a forged opaque identifier. Elasticsearch decodes and deserializes the identifier before confirming that it was legitimately issued by the cluster, and a size value carried inside the identifier drives an allocation that is neither capped nor accounted for by the available memory-usage controls. The resulting out-of-memory condition is fatal and terminates the affected node process, resulting in a denial of service.
Affected Versions:
- All versions from 8.0.0 up to and including 8.19.19
- All versions from 9.0.0 up to and including 9.4.4
- Version 9.5.0
Affected Configurations:
- All configurations are affected.
Solutions and Mitigations:
The issue is resolved in version 8.19.20, 9.4.5, and 9.5.1.
For Users that Cannot Upgrade:
There are no workarounds for this vulnerability.
Indicators of Compromise (IOC)
There are no identified indicators of compromise for this issue.
Elastic Cloud Serverless
Due to our continuous deployment and patching model, the vulnerability described in this security advisory was remediated in our Elastic Cloud Serverless offering before the public disclosure.
Severity: CVSSv3.1: Medium ( 6.5 ) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVE ID: CVE-2026-72687
Problem Type: CWE-789 - Memory Allocation with Excessive Size Value