CVE-2025-52887
📋 TL;DR
CVE-2025-52887 is a memory exhaustion vulnerability in cpp-httplib where excessive HTTP headers cause memory leaks when connections disconnect, potentially crashing servers. This affects any application using vulnerable versions of this C++ HTTP library. Attackers can exploit this to cause denial of service.
💻 Affected Systems
- cpp-httplib
📦 What is this software?
Cpp Httplib by Yhirose
⚠️ Risk & Real-World Impact
Worst Case
Complete server crash and denial of service, potentially affecting multiple services if the server hosts multiple applications.
Likely Case
Server becomes unresponsive or crashes under sustained attack, requiring manual restart and causing service disruption.
If Mitigated
Minimal impact with proper monitoring and rapid response to memory exhaustion alerts.
🎯 Exploit Status
Exploitation requires sending HTTP requests with many header fields. No authentication is needed if the service accepts HTTP requests. The advisory provides technical details but no public exploit code.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.22.0
Vendor Advisory: https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-xjhg-gf59-p92h
Restart Required: Yes
Instructions:
1. Update cpp-httplib to version 0.22.0 or later. 2. Recompile any applications using the library. 3. Restart affected services. 4. Verify the fix by checking the version in use.
🔧 Temporary Workarounds
Rate limiting and header size restrictions
allImplement network-level controls to limit request rate and header size before requests reach vulnerable applications
Reverse proxy with request filtering
linuxDeploy a reverse proxy (nginx, Apache, etc.) that filters requests with excessive headers before they reach the vulnerable service
nginx config example: client_header_buffer_size 1k; large_client_header_buffers 4 8k;
🧯 If You Can't Patch
- Deploy network-level protections like WAFs or load balancers to filter requests with excessive headers
- Implement aggressive monitoring for memory usage spikes and automated restart procedures for affected services
🔍 How to Verify
Check if Vulnerable:
Check if your application uses cpp-httplib version 0.21.0 by examining source code dependencies or build configurationsCheck Version:
Check your build system or package manager for cpp-httplib version. For source builds: grep -r "cpp-httplib" in source code to find version references.Verify Fix Applied:
Verify the application is using cpp-httplib version 0.22.0 or later and test with requests containing many headers to ensure memory doesn't leak📡 Detection & Monitoring
Log Indicators:
- Unusual number of HTTP requests with many headers
- Memory usage spikes followed by service crashes or restarts
- Error logs indicating memory allocation failures
Network Indicators:
- HTTP requests with hundreds of header fields
- Sustained high-volume requests to specific endpoints
- Abnormal request patterns from single IPs
SIEM Query:
source="web_server_logs" AND (header_count>100 OR request_size>8192) | stats count by src_ip