---
id: CVE-2023-5379
title: A flaw was found in Undertow
summary: >-
  A flaw was found in Undertow. When an AJP request is sent that exceeds the
  max-header-size attribute in ajp-listener, JBoss EAP is marked in an error
  state by mod_cluster in httpd, causing JBoss EAP to close the TCP connection
  without re…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-770
  - CWE-770
vendor: redhat
product: jboss_enterprise_application_platform
affected:
  - jboss_enterprise_application_platform
  - jboss_enterprise_application_platform = 7.0.0
  - single_sign-on = 7.0
  - undertow
published: '2023-12-12'
updated: '2026-08-04'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2023-5379'
references:
  - url: 'https://access.redhat.com/errata/RHSA-2025:9582'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2025:9583'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/security/cve/CVE-2023-5379'
    label: secalert@redhat.com
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2242099'
    label: secalert@redhat.com
  - url: 'https://access.redhat.com/errata/RHSA-2023:4509'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://access.redhat.com/security/cve/CVE-2023-5379'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2242099'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.01016
epssPercentile: 0.6174
ingestedAt: '2026-08-04T22:42:37.723Z'
---

## Overview

A flaw was found in Undertow. When an AJP request is sent that exceeds the max-header-size attribute in ajp-listener, JBoss EAP is marked in an error state by mod_cluster in httpd, causing JBoss EAP to close the TCP connection without returning an AJP response. This happens because mod_proxy_cluster marks the JBoss EAP instance as an error worker when the TCP connection is closed from the backend after sending the AJP request without receiving an AJP response, and stops forwarding. This issue could allow a malicious user could to repeatedly send requests that exceed the max-header-size, causing a Denial of Service (DoS).

## Affected

- `jboss_enterprise_application_platform`
- `jboss_enterprise_application_platform = 7.0.0`
- `single_sign-on = 7.0`
- `undertow`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.