Apache MINA Vysper 0.7 Unbounded XML Buffer Pre-Auth DoS


Vendor: The Apache Software Foundation
Product web page: https://mina.apache.org
Affected version: 0.7

Summary: Apache Vysper is an XMPP (eXtensible Messaging and
Presence Protocol) server, also known as Jabber, designed to
run stand-alone or embedded in another application and work
with any compliant XMPP client.

Desc: Apache MINA Vysper is an XMPP server that suffers from a
remote, unauthenticated denial-of-service vulnerability caused
by an unbounded XML buffer in its nbxml parser. The XMLTokenizer
accumulates incoming bytes into an auto-expanding buffer with no
maximum token, stanza, or request size, resetting it only when a
token's terminating delimiter is seen. A remote attacker can stream
a single very large XML token and grow the server heap until the
JVM throws OutOfMemoryError.

The vector is reachable over TCP XMPP (default port 5222), by
sending a stream header followed by an endless run of character
data with no closing delimiter, and over BOSH / XMPP-over-HTTP
(default port 8080), where the request decoder reads the entire
HTTP request body into memory before parsing, so a single large
HTTP POST is sufficient. Parsing runs on the first bytes received,
before authentication, so no credentials are required, and because
a single JVM serves all sessions the resulting OutOfMemoryError takes
down the entire server for every connected user.

Tested on: Microsoft Windows 10 (amd64)
           Eclipse Temurin (Adoptium) OpenJDK 21.0.6 (64-bit)
           nbxml 0.7
           mina-core 2.0.21
           slf4j-api 1.7.36


Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
                            @zeroscience


Advisory ID: ZSL-2026-6022
Advisory URL: https://www.zeroscience.mk/#/advisories/ZSL-2026-6022


13.08.2026

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$ head -c 3000000000 /dev/zero | curl -s -X POST -T - http://mina.vysper.sillysec.com:8080