CVE-2021-22885
📋 TL;DR
This vulnerability in Ruby on Rails Action Pack allows attackers to perform information disclosure or unintended method execution when using redirect_to or polymorphic_url helpers with untrusted user input. It affects Ruby on Rails applications using Action Pack version 2.0.0 and later. Attackers can potentially redirect users to malicious sites or execute unintended controller methods.
💻 Affected Systems
- Ruby on Rails Action Pack
📦 What is this software?
Rails by Rubyonrails
Rails by Rubyonrails
Rails by Rubyonrails
⚠️ Risk & Real-World Impact
Worst Case
Full application compromise through remote code execution or sensitive data exfiltration via crafted redirects
Likely Case
Open redirect attacks leading to phishing, session theft, or limited information disclosure
If Mitigated
Minimal impact with proper input validation and URL sanitization in place
🎯 Exploit Status
Exploitation requires crafting malicious URLs that get passed to vulnerable helpers
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.1.3.2, 6.0.3.7, 5.2.4.6, 5.1.7
Vendor Advisory: https://weblog.rubyonrails.org/2021/5/5/Rails-6-1-3-2-6-0-3-7-5-2-4-6-and-5-1-7-have-been-released/
Restart Required: Yes
Instructions:
1. Update Gemfile to specify patched Rails version. 2. Run 'bundle update rails'. 3. Restart application server. 4. Test redirect functionality.
🔧 Temporary Workarounds
Input Validation Workaround
allValidate and sanitize all user input before passing to redirect_to or polymorphic_url helpers
URL Whitelisting
allImplement URL whitelisting for redirect destinations
🧯 If You Can't Patch
- Implement strict input validation for all user-provided URLs
- Use WAF rules to detect and block malicious redirect patterns
🔍 How to Verify
Check if Vulnerable:
Check Rails version with 'rails --version' or examine Gemfile.lock for Action Pack versionCheck Version:
rails --versionVerify Fix Applied:
Verify Rails version is >= 6.1.3.2, 6.0.3.7, 5.2.4.6, or 5.1.7 depending on your major version📡 Detection & Monitoring
Log Indicators:
- Unusual redirect patterns
- Redirects to external domains from user input
- Multiple failed redirect attempts
Network Indicators:
- HTTP 302 redirects to suspicious domains
- URLs with encoded payloads in redirect parameters
SIEM Query:
event_type:web_access AND (status_code:302 OR status_code:301) AND url:*redirect* AND NOT destination_domain:trusted_domains