Medium [CVE-2026-14180] Undertow:HTTP request smuggling via oversized chunk-size bit overlap

A flaw was found in the ChunkReader component of the Undertow HTTP server, which is used by WildFly and JBoss EAP to handle chunked transfer encoding. The issue occurs because the parser uses a single internal variable to store both the remaining chunk size and state flags.

By sending a specially crafted request with an extremely large chunk size, an attacker can cause these values to overlap, tricking the parser into thinking a request has finished prematurely. This can allow a second, "smuggled" request to be processed out of sync, potentially bypassing security controls.

The Red Hat Product Security team has assessed the severity of this vulnerability as Moderate, given that exploitation requires a frontend proxy to forward oversized, non-standard chunk-size values to the backend Undertow server. Successful exploitation allows an attacker to perform HTTP request smuggling, leading to request desynchronization.

The vulnerability's root cause is an internal bitmask overlap in the ChunkReader state management logic where large chunk-size values collide with internal parser flags. Weakness: CWE-444.

Affected products named by the advisory: Red Hat build of Apache Camel for Spring Boot 4; Red Hat build of Apache Camel - HawtIO 4; Red Hat Data Grid 8; Red Hat Enterprise Linux 10; and 9 more.