A vulnerability was found in Undertow where the WebSocketContainer and its boot process do not allow setting the binaryBuffer and textBuffer sizes, along with session duration and async send timeout. These parameters default to infinite. This is a follow-up to CVE-2026-5680, as the initial fix allowed setting buffer sizes for certain types but left async send and session duration as infinite and inaccessible for configuration. An attacker could exploit these infinite defaults to cause resource exhaustion or an Out of Memory (OOME) condition on the server.
in depth analysis: https://docs.google.com/document/d/1XdX8AJzGjBgCLE0UZ5NRGGrzQ14HSVS8HcDgH0X70w/edit?tab=t.d440c4doqxdr#bookmark=kix.axzzwc7bbq6o
An external security assessment of Red Hat JBoss EAP 7 identified that the Undertow AJP listener on default port 8009 honours forged sslcert and isssl AJP attributes without requiring any shared-secret authentication. This enables an unauthenticated attacker with direct TCP access to port 8009 to bypass CLIENT-CERT authentication by injecting a forged X.509 certificate via the AJP protocol.
A flaw was found in Jastow. Jastow is vulnerable to Cross-Site Scripting (XSS) attack. If using a set of combined configuration to allow unescaped characters in URL with embedded Undertow and Jastow, a server might be vulnerable to improper input handling.
The undertow client is not checking the server identity presented by the server certificate in https connections. This is a compulsory step (at least it should be performed by default) in https and in http/2. I would add it to any TLS client protocol. https://issues.redhat.com/browse/UNDERTOW-2212
A flaw was found in Undertow where a potential security issue in flow control handling by browser over HTTP/2 may potentially cause overhead or DOS in the server. The highest impact of this vulnerability is availability.(incomplete fix for CVE-2021-3629)
A vulnerability was found in Undertow where buffer leak on incoming websocket PONG message may lead to memory exhaustion.
https://issues.redhat.com/browse/UNDERTOW-1935
It was found that the AJP connector in undertow does not use the ALLOWENCODEDSLASH option and thus allow the the slash / anti-slash characters encoded in the url which may lead to path traversal and result in the information disclosure of arbitrary local files.
Undertow keeps a cache of seen HTTP headers in persistent connections. It was found that this cache can easily exploited to fill memory with garbage, up to "max-headers" (default 200) "max-header-size" (default 1MB) per active TCP connection.
Upstream bug:
https://issues.jboss.org/browse/WFLY-7725