Description
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.
References6
Metrics
- CVSS 3.1
-
5.3
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N - EPSS — exploit probability
- 1% percentile: 64 · as of 12 November 2026
- CWE
- CWE-444
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.