# Logstash 8.17.6, 8.18.1, and 9.0.1 Security Update (ESA-2025-08)

**URL:** https://discuss.elastic.co/t/logstash-8-17-6-8-18-1-and-9-0-1-security-update-esa-2025-08/377869
**Category:** Security Announcements
**Created:** [May 6, 2025, 4:33pm UTC](https://discuss.elastic.co/t/logstash-8-17-6-8-18-1-and-9-0-1-security-update-esa-2025-08/377869 "2025-05-06T16:33:44Z")
**Posts on this page:** 1
**Page:** 1

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### Author: ![ismisepaul](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/ismisepaul/32/102235_2.png) [@ismisepaul](https://discuss.elastic.co/u/ismisepaul)
#### Post date: [May 6, 2025, 4:33pm UTC](https://discuss.elastic.co/t/logstash-8-17-6-8-18-1-and-9-0-1-security-update-esa-2025-08/377869/1 "2025-05-06T16:33:44Z")

</div>

**Logstash Improper Certificate Validation in TCP output (ESA-2025-08)**

Improper certificate validation in Logstash's TCP output could lead to a man-in-the-middle (MitM) attack in “client” mode, as hostname verification in TCP output was not being performed when the `ssl_verification_mode => full` was set.

**Affected Versions:**  
All versions prior to 8.17.6, as well as version 8.18.0 and version 9.0.0.

**Affected Configurations:**  
This issue affects the TCP output plugin when run in “client” mode and `ssl_verification_mode => full` is set to `full` (the default).

**Solutions and Mitigations:**  
The issue is resolved in version 8.17.6, 8.18.1, and 9.0.1.

Alternatively, users may also upgrade the TCP output plugin to 6.2.2 or 7.0.1 by running `bin/logstash-plugin update logstash-output-tcp`.

**Severity:** CVSSv3.1: 5.9 (Medium) - [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N](https://www.first.org/cvss/calculator/3-1#CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N)  
**CVE ID:** CVE-2025-37730