CVE-2023-39685
📋 TL;DR
This vulnerability in hjson-java allows attackers to cause Denial of Service (DoS) by sending specially crafted JSON strings. Applications using hjson-java for JSON parsing are affected when processing untrusted input. The vulnerability enables resource exhaustion attacks that can crash or degrade service availability.
💻 Affected Systems
- hjson-java
📦 What is this software?
Hjson by Hjson
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability requiring manual restart, potentially affecting all users of the application.
Likely Case
Service degradation or temporary unavailability affecting users processing malicious JSON input.
If Mitigated
Minimal impact with proper input validation and resource limits in place.
🎯 Exploit Status
Exploitation requires sending crafted JSON to vulnerable endpoints. No authentication needed if application accepts JSON input from untrusted sources.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v3.1.0 or later
Vendor Advisory: https://github.com/hjson/hjson-java/issues/27
Restart Required: Yes
Instructions:
1. Update hjson-java dependency to v3.1.0 or later in your project's build configuration (pom.xml for Maven, build.gradle for Gradle). 2. Rebuild and redeploy your application. 3. Restart affected services.
🔧 Temporary Workarounds
Input Validation and Size Limits
allImplement strict input validation and size limits on JSON payloads before passing to hjson-java parser.
Rate Limiting
allImplement rate limiting on JSON processing endpoints to prevent mass exploitation attempts.
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block suspicious JSON payloads
- Isolate vulnerable services behind reverse proxies with request filtering capabilities
🔍 How to Verify
Check if Vulnerable:
Check your project's dependency management file (pom.xml or build.gradle) for hjson-java version. If version is 3.0.0 or earlier, you are vulnerable.Check Version:
For Maven: mvn dependency:tree | grep hjson-java; For Gradle: gradle dependencies | grep hjson-javaVerify Fix Applied:
After updating, verify the hjson-java version in your dependencies is 3.1.0 or later. Test JSON parsing functionality with various inputs.📡 Detection & Monitoring
Log Indicators:
- Unusual memory consumption spikes
- Application crashes or restarts during JSON processing
- Exception stack traces containing hjson-java classes
Network Indicators:
- Large or malformed JSON payloads to JSON processing endpoints
- High volume of requests to JSON endpoints
SIEM Query:
source="application.logs" AND ("OutOfMemoryError" OR "StackOverflowError") AND "hjson"