# Elasticsearch 8.19.20, 9.4.5, 9.5.1 Security Update (ESA-2026-80)

**URL:** <https://discuss.elastic.co/t/elasticsearch-8-19-20-9-4-5-9-5-1-security-update-esa-2026-80/389507>\
**Category:** Security Announcements\
**Created:** [August 13, 2026, 10:47am UTC](https://discuss.elastic.co/t/elasticsearch-8-19-20-9-4-5-9-5-1-security-update-esa-2026-80/389507 "2026-08-13T10:47:26Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ikakavas](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ikakavas/32/34430_2.png) [@ikakavas](https://discuss.elastic.co/u/ikakavas)\
**Post date:** [August 13, 2026, 10:47am UTC](https://discuss.elastic.co/t/elasticsearch-8-19-20-9-4-5-9-5-1-security-update-esa-2026-80/389507/1 "2026-08-13T10:47:26Z")

</div>

**Memory Allocation with Excessive Size Value in Elasticsearch Leading to Denial of Service**

Elasticsearch does not validate a size value taken from a user-supplied input before that value is used to reserve memory for an internal data structure. An authenticated user holding only read privileges can submit a single small crafted request to a product API endpoint that causes the node to attempt an excessively large allocation. The resulting memory exhaustion raises a fatal error that terminates the Elasticsearch node process, causing a denial of service for the affected node and degrading cluster health. The defect is not volumetric, so a single request is sufficient regardless of the heap size configured on the target node.

**Affected Versions:**

> - All versions from 8.19.0 up to and including 8.19.19
> - All versions from 9.4.0 up to and including 9.4.4
> - Version 9.5.0

**Affected Configurations:**

> - All Elasticsearch deployments running an affected version where an attacker can authenticate to the REST API
> - The attacker requires only a role granting read privileges; no write, cluster, or administrative privileges are needed

**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)**

Unexpected termination of an Elasticsearch node process, accompanied by a fatal out-of-memory error recorded in the Elasticsearch server log immediately before the process exits, may indicate exploitation of this vulnerability.

**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-2026-72678  
**Problem Type:** CWE-789 - Memory Allocation with Excessive Size Value