CVE-2023-48840
📋 TL;DR
This vulnerability in Appointment Scheduler 3.0 allows attackers to send unlimited AJAX requests to the pjActionAjaxSend endpoint, causing resource exhaustion through denial of service. Any organization using the vulnerable version of this PHP-based scheduling software is affected.
💻 Affected Systems
- PHP Jabbers Appointment Scheduler
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete service unavailability due to resource exhaustion, preventing legitimate users from accessing appointment scheduling functionality.
Likely Case
Degraded performance and intermittent service disruptions affecting appointment booking and management.
If Mitigated
Minimal impact with proper rate limiting and monitoring in place.
🎯 Exploit Status
Simple HTTP flood attack against the vulnerable endpoint. No authentication required.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after 3.0 (check vendor for specific version)
Vendor Advisory: https://www.phpjabbers.com/appointment-scheduler/
Restart Required: No
Instructions:
1. Backup current installation. 2. Download latest version from PHP Jabbers. 3. Replace vulnerable files with patched version. 4. Test functionality.
🔧 Temporary Workarounds
Web Server Rate Limiting
allImplement rate limiting at web server level for the vulnerable endpoint
# Apache: Use mod_ratelimit or mod_security
# Nginx: limit_req_zone $binary_remote_addr zone=appointment:10m rate=10r/s;
# Then apply to location: limit_req zone=appointment burst=20 nodelay;
WAF Rule
linuxAdd Web Application Firewall rule to limit requests to pjActionAjaxSend
# Example mod_security rule:
SecRule REQUEST_URI "@contains pjActionAjaxSend" \
"id:1001,phase:1,deny,status:429,msg:'Rate limit exceeded'" \
"chain"
SecRule &IP:APPOINTMENT_RATE "@eq 1" \
"setvar:'ip.appointment_rate=+1',expirevar:'ip.appointment_rate=60'"
SecRule IP:APPOINTMENT_RATE "@gt 100" \
"setvar:'tx.anomaly_score=+%{tx.critical_anomaly_score}'"
🧯 If You Can't Patch
- Implement network-level rate limiting using firewall or load balancer
- Monitor for abnormal request patterns to the vulnerable endpoint
🔍 How to Verify
Check if Vulnerable:
Check if Appointment Scheduler version is 3.0 and if pjActionAjaxSend endpoint is accessible without rate limitingCheck Version:
Check version.php or CHANGELOG.txt in installation directoryVerify Fix Applied:
Test that rapid requests to pjActionAjaxSend endpoint are properly rate limited or blocked📡 Detection & Monitoring
Log Indicators:
- High frequency of requests to pjActionAjaxSend endpoint
- 429 status codes if rate limiting is implemented
- Resource exhaustion errors in server logs
Network Indicators:
- Unusual high volume of HTTP POST requests to appointment scheduler
- Traffic spikes from single IP addresses
SIEM Query:
source="web_server_logs" | where url contains "pjActionAjaxSend" | stats count by src_ip | where count > 100