CVE-2025-53629
📋 TL;DR
This vulnerability in cpp-httplib allows attackers to send specially crafted HTTP requests with Transfer-Encoding: chunked headers that cause uncontrolled memory allocation, potentially leading to server memory exhaustion and denial of service. It affects all systems using cpp-httplib versions before 0.23.0 that process HTTP requests.
💻 Affected Systems
- cpp-httplib
📦 What is this software?
Cpp Httplib by Yhirose
⚠️ Risk & Real-World Impact
Worst Case
Complete server memory exhaustion leading to denial of service, potentially causing application crashes and service unavailability.
Likely Case
Degraded server performance, memory exhaustion, and denial of service affecting application availability.
If Mitigated
Limited impact with proper memory limits and monitoring, but still vulnerable to targeted attacks.
🎯 Exploit Status
Exploitation requires sending HTTP requests with Transfer-Encoding: chunked headers, which is straightforward for attackers with network access to vulnerable servers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.23.0
Vendor Advisory: https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-j6p8-779x-p5pw
Restart Required: Yes
Instructions:
1. Update cpp-httplib to version 0.23.0 or later. 2. Replace the single header file in your project with the patched version. 3. Recompile and restart your application.
🔧 Temporary Workarounds
Implement request size limits
allConfigure HTTP server to limit maximum request size and chunk sizes
// In cpp-httplib server configuration, set request size limits
svr.set_payload_max_length(1048576); // Example: 1MB limit
Filter Transfer-Encoding headers
allImplement middleware to reject or sanitize Transfer-Encoding headers
// Add request handler to check headers
svr.Post("/", [](const Request &req, Response &res) {
if (req.has_header("Transfer-Encoding")) {
res.status = 400; // Bad Request
return;
}
// Process request normally
});
🧯 If You Can't Patch
- Implement network-level protections such as WAF rules to block or limit Transfer-Encoding: chunked requests
- Deploy memory monitoring and alerting to detect abnormal memory consumption patterns
🔍 How to Verify
Check if Vulnerable:
Check if your application uses cpp-httplib version earlier than 0.23.0 by examining the header file version or build configuration.Check Version:
grep -n "CPPHTTPLIB_VERSION" httplib.h | head -1Verify Fix Applied:
Verify the cpp-httplib header file contains the fix from commit 17ba303889b8d4d719be3879a70639ab653efb99 and version is 0.23.0 or higher.📡 Detection & Monitoring
Log Indicators:
- Unusually large memory consumption by HTTP server process
- Multiple HTTP requests with Transfer-Encoding: chunked headers
- Server crashes or restarts following HTTP requests
Network Indicators:
- HTTP requests with Transfer-Encoding: chunked headers to vulnerable endpoints
- Abnormally large HTTP request payloads
SIEM Query:
source="web_server" AND (http_header="Transfer-Encoding: chunked" OR memory_usage>90%)🔗 References
- https://github.com/yhirose/cpp-httplib/commit/17ba303889b8d4d719be3879a70639ab653efb99
- https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-j6p8-779x-p5pw
- https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-qjmq-h3cc-qv6w
- https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-qjmq-h3cc-qv6w
