Vulnerability Description
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.37.1, when a cpp-httplib client uses the streaming API (httplib::stream::Get, httplib::stream::Post, etc.), the library calls std::stoull() directly on the Content-Length header value received from the server with no input validation and no exception handling. std::stoull throws std::invalid_argument for non-numeric strings and std::out_of_range for values exceeding ULLONG_MAX. Since nothing catches these exceptions, the C++ runtime calls std::terminate(), which kills the process with SIGABRT. Any server the client connects to — including servers reached via HTTP redirects, third-party APIs, or man-in-the-middle positions can crash the client application with a single HTTP response. No authentication is required. No interaction from the end user is required. The crash is deterministic and immediate. This vulnerability is fixed in 0.37.1.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Yhirose | Cpp-Httplib | < 0.37.1 |
Related Weaknesses (CWE)
References
- https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-39q5-hh6x-jpxxExploitMitigationVendor Advisory
FAQ
What is CVE-2026-31870?
CVE-2026-31870 is a vulnerability with a CVSS score of 7.5 (HIGH). cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.37.1, when a cpp-httplib client uses the streaming API (httplib::stream::Get, httplib::stream::Post, etc.),...
How severe is CVE-2026-31870?
CVE-2026-31870 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-31870?
Check the references section above for vendor advisories and patch information. Affected products include: Yhirose Cpp-Httplib.