CVE-2026-3813: Opencc Jflow RCE Vulnerability

CVE-2026-3813 Overview

An injection vulnerability has been identified in opencc JFlow, a workflow management platform. The vulnerability exists in the Calculate function within the file src/main/java/bp/wf/httphandler/WF_CCForm.java. This security flaw allows attackers to inject malicious input that can be processed by the application, potentially leading to unauthorized actions or data manipulation. The attack can be performed remotely over the network by authenticated users with low privileges.

Critical Impact

Remote injection attacks can compromise application integrity, potentially allowing attackers to manipulate workflow data, execute arbitrary commands, or gain unauthorized access to sensitive information processed by the JFlow workflow system.

Affected Products

• opencc JFlow (all versions up to commit 5badc00db382d7cb82dad231e6a866b18e0addfe)
• JFlow workflow management deployments using the vulnerable WF_CCForm handler
• Systems running JFlow with the affected Calculate function exposed to network access

Discovery Timeline

• 2026-03-09 - CVE-2026-3813 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-3813

Vulnerability Analysis

This vulnerability is classified under CWE-74 (Improper Neutralization of Special Elements in Output Used by a Downstream Component, or 'Injection') and CWE-77 (Command Injection). The Calculate function in WF_CCForm.java fails to properly sanitize or validate user-supplied input before processing it. This allows attackers to inject specially crafted payloads that are interpreted as commands or queries by the application.

The vulnerability can be exploited remotely over the network. An attacker with low-level privileges (authenticated user) can submit malicious input to the vulnerable endpoint. The attack requires no user interaction and has low complexity, making it relatively straightforward to exploit once an attacker has identified the vulnerable function.

The impact includes potential compromise of data confidentiality, integrity, and availability at a limited scope. While the vulnerability does not appear to affect other components beyond the vulnerable application itself, successful exploitation could allow attackers to read sensitive workflow data, modify calculations or workflow states, or cause service disruption.

Root Cause

The root cause of this vulnerability lies in improper input validation and sanitization within the Calculate function. The function processes user-supplied data without adequately neutralizing special characters or elements that could be interpreted as control sequences. This lack of input validation allows injection payloads to be processed as legitimate commands or query elements.

JFlow uses a rolling release development model, which means specific version numbers are not assigned to releases. The vulnerability affects all versions up to and including commit 5badc00db382d7cb82dad231e6a866b18e0addfe. The project maintainers were notified of the issue through a Gitee issue report, but have not yet responded.

Attack Vector

The attack vector is network-based, requiring authenticated access to the JFlow application. An attacker can exploit this vulnerability by:

1. Authenticating to the JFlow application with low-privilege credentials
2. Crafting a malicious request targeting the WF_CCForm handler
3. Injecting specially formatted input into parameters processed by the Calculate function
4. The malicious input bypasses insufficient validation and is processed by downstream components

The vulnerability manifests in the Calculate function's input handling mechanism. The function accepts user-controlled data that is processed without proper sanitization, allowing injection of command sequences. Detailed technical information about the vulnerability is available in the Gitee Issue Report and VulDB entry #349779.

Detection Methods for CVE-2026-3813

Indicators of Compromise

• Unusual or malformed requests to the WF_CCForm endpoint containing special characters or injection patterns
• Unexpected command execution or system calls originating from the JFlow application process
• Anomalous database queries or data modifications associated with the Calculate function
• Error logs showing parsing failures or injection-related exceptions in WF_CCForm.java

Detection Strategies

• Implement web application firewall (WAF) rules to detect common injection patterns targeting the WF_CCForm handler
• Monitor HTTP request logs for suspicious payloads containing command injection characters (;, |, &&, backticks)
• Deploy application-layer intrusion detection to identify anomalous behavior in the Calculate function
• Enable verbose logging for the JFlow httphandler components to capture detailed request information

Monitoring Recommendations

• Configure alerting for unusual traffic patterns to the JFlow workflow endpoints
• Implement real-time log analysis for the bp.wf.httphandler package to detect exploitation attempts
• Monitor system process spawning from the JFlow application server for signs of command execution
• Track authentication events and correlate with suspicious requests to identify compromised accounts

How to Mitigate CVE-2026-3813

Immediate Actions Required

• Review and restrict network access to JFlow instances, limiting exposure to trusted networks only
• Implement input validation at the application or WAF level to filter injection payloads
• Monitor the Gitee Issue Report for vendor response and patch availability
• Audit user accounts with access to JFlow and enforce least-privilege principles
• Consider temporarily disabling or restricting access to the WF_CCForm functionality if not critical

Patch Information

As of the last update on 2026-03-10, no official patch has been released by the opencc project maintainers. The project uses a rolling release model without discrete version numbers, making it essential to monitor the official JFlow repository for commits addressing this vulnerability. The issue was reported through the Gitee platform, but the project has not yet responded.

Organizations should subscribe to updates from the VulDB entry and the Gitee repository to receive notification when a fix becomes available.

Workarounds

• Deploy a web application firewall (WAF) with rules to block common injection patterns targeting the vulnerable endpoint
• Implement network segmentation to isolate JFlow instances from untrusted networks
• Apply custom input validation filters at the reverse proxy or load balancer level
• Restrict access to the WF_CCForm handler to only essential users through access control lists
• Consider implementing runtime application self-protection (RASP) to detect and block injection attempts

# Example WAF rule configuration (ModSecurity format)
# Block potential injection attempts to WF_CCForm endpoint
SecRule REQUEST_URI "@contains WF_CCForm" \
    "id:100001,phase:2,deny,status:403,\
    chain"
SecRule ARGS "@detectSQLi" \
    "id:100002,phase:2,deny,status:403,\
    msg:'Potential injection attempt blocked'"