What’s Vulnerable › Vulnerabilities
CVE-2026-31870: cpp-httplib Affected by Remote Process Crash via Malformed Content-Length Response Header
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.5% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2026-03-11 · updated 2026-06-17
- Weakness: CWE-248
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.
Affected products
- yhirose cpp-httplib: before 0.37.1 — fixed in 0.37.1
How to fix
Upgrade to a fixed version: yhirose cpp-httplib 0.37.1. Check the vendor advisory for mitigations.
References
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