CVE-2023-40175
📋 TL;DR
This CVE describes an HTTP request smuggling vulnerability in Puma web server that allows attackers to bypass security controls by sending specially crafted HTTP requests. The vulnerability affects Puma servers running versions before 6.3.1 and 5.6.7, potentially enabling attackers to poison caches, bypass authentication, or access restricted resources.
💻 Affected Systems
- Puma web server
📦 What is this software?
Puma by Puma
Puma by Puma
⚠️ Risk & Real-World Impact
Worst Case
Attackers could poison web caches, bypass authentication mechanisms, perform account takeover, or access sensitive backend systems through request smuggling attacks.
Likely Case
Cache poisoning leading to stored XSS, authentication bypass for specific endpoints, or access to internal APIs not intended for public consumption.
If Mitigated
Limited impact if proper WAF rules are in place and backend systems have additional authentication layers, though request smuggling could still bypass some perimeter controls.
🎯 Exploit Status
Exploitation requires crafting specific HTTP requests with chunked transfer encoding or zero-length Content-Length headers. No public exploit code is known at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.3.1 or 5.6.7
Vendor Advisory: https://github.com/puma/puma/security/advisories/GHSA-68xg-gqqm-vgj8
Restart Required: Yes
Instructions:
1. Update Gemfile to specify puma version '>=6.3.1' or '>=5.6.7'. 2. Run 'bundle update puma'. 3. Restart the Puma server process. 4. Verify the update with 'bundle show puma'.
🔧 Temporary Workarounds
No workarounds available
allThe vendor advisory states there are no known workarounds for this vulnerability
🧯 If You Can't Patch
- Implement a WAF with HTTP request smuggling protection rules
- Deploy a reverse proxy with request normalization that validates and sanitizes HTTP headers before forwarding to Puma
🔍 How to Verify
Check if Vulnerable:
Check Puma version with 'bundle show puma' or 'gem list puma'. If version is below 6.3.1 (for Puma 6.x) or below 5.6.7 (for Puma 5.x), the system is vulnerable.Check Version:
bundle show puma | grep pumaVerify Fix Applied:
After updating, verify with 'bundle show puma' that version is 6.3.1 or higher (for 6.x) or 5.6.7 or higher (for 5.x).📡 Detection & Monitoring
Log Indicators:
- Multiple requests with same request ID but different content
- Unexpected 400/413 errors from backend systems
- Requests with malformed Transfer-Encoding or Content-Length headers
Network Indicators:
- HTTP requests with both Transfer-Encoding: chunked and Content-Length headers
- Requests with zero-length Content-Length headers
- Abnormal request/response timing patterns
SIEM Query:
source="puma.log" AND ("Transfer-Encoding" AND "Content-Length") OR ("Content-Length: 0")