CVE-2023-49316
📋 TL;DR
This vulnerability in phpseclib 3 allows attackers to cause denial of service by providing excessively large degree values to BinaryField.php. It affects applications using phpseclib for cryptographic operations. The vulnerability can be exploited remotely if the affected component is exposed to user input.
💻 Affected Systems
- phpseclib
📦 What is this software?
Phpseclib by Phpseclib
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability due to resource exhaustion, potentially affecting all users of the application.
Likely Case
Degraded performance or temporary service disruption for specific users or functions.
If Mitigated
Minimal impact with proper input validation and resource limits in place.
🎯 Exploit Status
Exploitation requires sending specially crafted input to the vulnerable component.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.0.34
Vendor Advisory: https://github.com/phpseclib/phpseclib/releases/tag/3.0.34
Restart Required: No
Instructions:
1. Update phpseclib to version 3.0.34 or later using composer: composer require phpseclib/phpseclib:^3.0.34
2. Verify the update completed successfully
3. Test affected functionality
🔧 Temporary Workarounds
Input validation
allImplement strict input validation to reject excessively large degree values before they reach BinaryField.php
Resource limits
allConfigure PHP memory and execution time limits to prevent resource exhaustion
php -i | grep memory_limit
php -i | grep max_execution_time
🧯 If You Can't Patch
- Implement WAF rules to block requests with suspiciously large numeric parameters
- Isolate the vulnerable component behind rate limiting and monitoring
🔍 How to Verify
Check if Vulnerable:
Check composer.json or vendor/phpseclib/phpseclib/VERSION file for version numberCheck Version:
composer show phpseclib/phpseclib | grep versionsVerify Fix Applied:
Confirm version is 3.0.34 or higher and test with known malicious inputs📡 Detection & Monitoring
Log Indicators:
- Unusually high memory usage
- PHP fatal errors related to memory exhaustion
- Long execution times for cryptographic operations
Network Indicators:
- Large numeric parameters in requests to cryptographic endpoints
- Repeated requests with varying large numbers
SIEM Query:
source="php_error.log" AND ("Allowed memory size" OR "memory exhausted") AND process="php"