CVE-2021-3804
📋 TL;DR
CVE-2021-3804 is a regular expression denial-of-service (ReDoS) vulnerability in Taro, a cross-platform development framework. Attackers can cause excessive CPU consumption and service degradation by sending specially crafted input to applications using vulnerable Taro versions. This affects developers and organizations using Taro for web or mobile applications.
💻 Affected Systems
- Taro
📦 What is this software?
Taro by Taro
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability due to CPU exhaustion, leading to denial of service for legitimate users and potential cascading failures in dependent systems.
Likely Case
Degraded application performance, increased response times, and potential service interruptions affecting user experience.
If Mitigated
Minimal impact with proper input validation, rate limiting, and updated versions; performance degradation limited to isolated instances.
🎯 Exploit Status
Exploitation requires sending malicious input to endpoints using vulnerable regex patterns; no authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.3.12 and later
Vendor Advisory: https://github.com/nervjs/taro/commit/acadb6c826ba57f2030a626f1de4f7b4608fcdb5
Restart Required: Yes
Instructions:
1. Update Taro to version 3.3.12 or later using npm: 'npm update @tarojs/taro'. 2. Rebuild and redeploy your application. 3. Restart any running services using Taro.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement strict input validation to reject or sanitize inputs that could trigger the vulnerable regex patterns.
Rate Limiting
allApply rate limiting to endpoints that process user input to reduce the impact of potential DoS attacks.
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block malicious input patterns targeting the vulnerability.
- Monitor CPU usage and application performance metrics for anomalies indicating exploitation attempts.
🔍 How to Verify
Check if Vulnerable:
Check your package.json or run 'npm list @tarojs/taro' to see if Taro version is below 3.3.12.Check Version:
npm list @tarojs/taro | grep @tarojs/taroVerify Fix Applied:
After updating, verify the version is 3.3.12 or higher with 'npm list @tarojs/taro' and test application functionality.📡 Detection & Monitoring
Log Indicators:
- Unusually high CPU usage spikes
- Increased error rates or timeouts in application logs
- Patterns of repeated requests with similar payloads
Network Indicators:
- High volume of requests to specific endpoints
- Abnormal request patterns with regex-like strings
SIEM Query:
source="application_logs" AND (cpu_usage > 90% OR error_rate > 10%) AND process="node"