CVE-2023-5379 Undertow: ajp request closes connection exceeding maxrequestsize

High 7.5 Published 12 Dec 2023 Updated 4 Aug 2026

Attackers can cause a Denial of Service by sending AJP requests exceeding the max-header-size, forcing the server to close connections without response.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2023-5379?

CVE-2023-5379 is a high-severity denial of service vulnerability in Redhat Jboss Enterprise Application Platform, published on 12 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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).

Weakness: CWE-770

Which versions are affected by CVE-2023-5379?

It affects 3 products.

Products include Redhat Jboss Enterprise Application Platform, Redhat Single Sign-On, Redhat Undertow.

How do I fix CVE-2023-5379?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2023-5379 being exploited?

There is no known exploitation of CVE-2023-5379 in the wild and no public exploit code.

All Redhat Jboss Enterprise Application Platform vulnerabilities

Sources

Also known as DEBIAN-CVE-2023-5379, GHSA-q462-4hrv-w27r, UBUNTU-CVE-2023-5379.