CVE-2021-31409
📋 TL;DR
CVE-2021-31409 is a denial-of-service vulnerability in Vaadin's EmailValidator component where unsafe regular expression validation allows attackers to submit malicious email addresses causing uncontrolled resource consumption. This affects applications using com.vaadin:vaadin-compatibility-server versions 8.0.0 through 8.12.4 (Vaadin 8.0.0 through 8.12.4). Attackers can cause application slowdowns or crashes by exploiting inefficient regex patterns.
💻 Affected Systems
- Vaadin Framework
- com.vaadin:vaadin-compatibility-server
📦 What is this software?
Vaadin by Vaadin
⚠️ Risk & Real-World Impact
Worst Case
Complete application unavailability due to resource exhaustion, potentially affecting all users and causing service disruption.
Likely Case
Degraded application performance, increased response times, and potential partial service interruption for affected endpoints.
If Mitigated
Minimal performance impact with proper input validation and rate limiting in place.
🎯 Exploit Status
Exploitation requires submitting specially crafted email addresses to vulnerable endpoints. Public proof-of-concept available in GitHub issues.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.13.0 or later
Vendor Advisory: https://vaadin.com/security/cve-2021-31409
Restart Required: Yes
Instructions:
1. Update com.vaadin:vaadin-compatibility-server dependency to version 8.13.0 or later. 2. Update pom.xml or build.gradle to reference patched version. 3. Rebuild and redeploy application. 4. Restart application server.
🔧 Temporary Workarounds
Input Validation Filter
allImplement custom input validation to reject or sanitize email addresses before they reach the vulnerable EmailValidator component.
Rate Limiting
allImplement rate limiting on email validation endpoints to prevent mass exploitation attempts.
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to block malicious regex patterns in email submissions
- Disable or replace the vulnerable EmailValidator component with a secure alternative
🔍 How to Verify
Check if Vulnerable:
Check pom.xml or build.gradle for com.vaadin:vaadin-compatibility-server version between 8.0.0 and 8.12.4 inclusive.Check Version:
mvn dependency:tree | grep vaadin-compatibility-server OR gradle dependencies | grep vaadin-compatibility-serverVerify Fix Applied:
Verify com.vaadin:vaadin-compatibility-server version is 8.13.0 or later in dependency files and deployed application.📡 Detection & Monitoring
Log Indicators:
- Unusually high CPU/memory usage on email validation endpoints
- Multiple failed email validation attempts with similar patterns
- Application logs showing regex timeout or stack overflow errors
Network Indicators:
- High volume of requests to email validation endpoints
- Requests containing specially crafted email addresses with regex patterns
SIEM Query:
source="application.logs" AND ("EmailValidator" OR "regex" OR "stack overflow") AND ("timeout" OR "high cpu" OR "denial")