CVE-2021-35514
📋 TL;DR
CVE-2021-35514 is a critical code injection vulnerability in Narou.rb that allows attackers to execute arbitrary Ruby code by manipulating novel title or author name fields. This affects all Narou.rb users running versions before 3.8.0, potentially leading to complete system compromise.
💻 Affected Systems
- Narou.rb (also known as Narou)
📦 What is this software?
Narou by Narou Project
⚠️ Risk & Real-World Impact
Worst Case
Full remote code execution leading to complete system takeover, data theft, and lateral movement within the network.
Likely Case
Arbitrary code execution with the privileges of the Narou.rb process, potentially allowing file system access, data manipulation, and further exploitation.
If Mitigated
Limited impact if proper input validation and sanitization are implemented, restricting code execution to sandboxed environments.
🎯 Exploit Status
Exploitation requires the ability to modify novel metadata, which typically requires some level of access to the system or data sources.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.8.0 and later
Vendor Advisory: https://github.com/whiteleaf7/narou/blob/develop/ChangeLog.md#380-20210627
Restart Required: Yes
Instructions:
1. Backup current configuration and data. 2. Update Narou.rb using 'gem update narou'. 3. Verify installation with 'narou version'. 4. Restart any Narou.rb services or processes.
🔧 Temporary Workarounds
Input Validation Filter
allImplement strict input validation to reject any novel titles or author names containing Ruby code patterns.
# Add input validation in Narou.rb configuration or wrapper scripts
# Example: Validate input doesn't contain eval(), system(), backticks, or Ruby execution patterns
🧯 If You Can't Patch
- Isolate Narou.rb instances in network segments with strict egress filtering
- Implement application-level firewalls to monitor and block suspicious input patterns
🔍 How to Verify
Check if Vulnerable:
Check Narou.rb version with 'narou version' command and verify it's below 3.8.0.Check Version:
narou versionVerify Fix Applied:
After updating, confirm version is 3.8.0 or higher with 'narou version' and test with known safe input.📡 Detection & Monitoring
Log Indicators:
- Unusual Ruby code execution in logs
- Suspicious novel metadata modifications
- Unexpected system command execution
Network Indicators:
- Unusual outbound connections from Narou.rb process
- Data exfiltration patterns
SIEM Query:
process: narou AND (command: *eval* OR command: *system* OR command: *backtick*)