CVE-2026-4735: DTStack ChunJun Deserialization Vulnerability

CVE-2026-4735 Overview

A Deserialization of Untrusted Data vulnerability has been identified in DTStack chunjun, specifically affecting the chunjun-core/src/main/java/com/dtstack/chunjun/util modules. This vulnerability is associated with the program file GsonUtil.java and allows remote attackers to potentially exploit insecure deserialization to cause denial of service conditions or impact the availability of downstream systems.

Critical Impact

This insecure deserialization vulnerability in DTStack chunjun can be exploited remotely without authentication, potentially leading to high availability impact on both vulnerable and subsequent systems.

Affected Products

• DTStack chunjun versions before 1.16.1
• chunjun-core module (GsonUtil.java)
• Applications utilizing vulnerable chunjun data integration components

Discovery Timeline

• 2026-03-24 - CVE-2026-4735 published to NVD
• 2026-03-24 - Last updated in NVD database

Technical Details for CVE-2026-4735

Vulnerability Analysis

This vulnerability falls under CWE-502 (Deserialization of Untrusted Data), a well-documented class of security flaws that occurs when an application deserializes data from untrusted sources without proper validation. In the context of DTStack chunjun, the vulnerability exists within the GsonUtil.java utility class, which is part of the core data transformation and processing pipeline.

The insecure deserialization flaw enables attackers to supply maliciously crafted serialized objects that, when processed by the vulnerable utility class, can trigger unintended behavior. This can result in resource exhaustion, application crashes, or cascading failures in connected systems that depend on chunjun for data integration tasks.

Root Cause

The root cause of this vulnerability lies in the improper handling of untrusted input during the deserialization process within GsonUtil.java. The utility class fails to adequately validate or sanitize incoming serialized data before processing, allowing attackers to inject malicious payloads. This is a common pattern in Java applications that use JSON deserialization libraries without implementing proper type restrictions or input validation safeguards.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker can craft malicious JSON payloads targeting the deserialization routines in the chunjun utility module. When the vulnerable application processes these payloads, it can lead to denial of service conditions affecting both the primary system and any downstream components that rely on chunjun's data processing capabilities.

The attack surface is particularly concerning in environments where chunjun is exposed to untrusted network segments or processes data from external sources. For detailed technical information about the vulnerability and the fix, refer to the GitHub Pull Request #1939.

Detection Methods for CVE-2026-4735

Indicators of Compromise

• Unexpected application crashes or restarts in services utilizing chunjun data integration
• Anomalous JSON payloads in network traffic destined for chunjun-based applications
• Increased memory consumption or resource exhaustion in Java processes running chunjun
• Error logs indicating deserialization failures or malformed object exceptions in GsonUtil operations

Detection Strategies

• Implement application-level logging to capture and analyze all deserialization operations within chunjun modules
• Deploy network intrusion detection rules to identify malicious serialized payloads targeting Java applications
• Monitor Java heap usage and garbage collection patterns for anomalies that may indicate exploitation attempts
• Utilize static code analysis tools to identify vulnerable deserialization patterns in applications using chunjun

Monitoring Recommendations

• Configure alerting for unusual error rates in chunjun-core module components
• Establish baselines for normal application behavior and alert on deviations in resource consumption
• Implement centralized logging for all chunjun-based services to correlate potential attack indicators
• Review application dependencies to identify all instances where vulnerable chunjun versions are deployed

How to Mitigate CVE-2026-4735

Immediate Actions Required

• Upgrade DTStack chunjun to version 1.16.1 or later immediately
• Audit all applications and data pipelines that utilize chunjun components for vulnerable versions
• Implement network segmentation to limit exposure of chunjun-based services to untrusted networks
• Review and restrict input sources that feed data into chunjun deserialization routines

Patch Information

The vulnerability has been addressed in DTStack chunjun version 1.16.1. The fix is documented in GitHub Pull Request #1939, which implements proper validation and sanitization of data during the deserialization process in GsonUtil.java.

Organizations should prioritize upgrading to the patched version across all environments where chunjun is deployed. Ensure that dependency management tools are updated to pull the corrected version and verify the upgrade through dependency scanning.

Workarounds

• Implement input validation at the application layer before data reaches chunjun deserialization routines
• Deploy Web Application Firewalls (WAF) with rules to filter malicious JSON payloads
• Restrict network access to chunjun-based services to trusted internal networks only
• Consider implementing Java Security Manager policies to limit the impact of deserialization attacks

# Verify chunjun version in Maven projects
mvn dependency:tree | grep chunjun

# Update chunjun dependency to patched version in pom.xml
# Change version to 1.16.1 or later:
# <dependency>
#   <groupId>com.dtstack</groupId>
#   <artifactId>chunjun-core</artifactId>
#   <version>1.16.1</version>
# </dependency>