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CVE-2026-31870

HIGH CVSS 3.1: 7.5 EPSS 0.07%
Updated Mar 18, 2026
Yhirose
Parameter Value
CVSS 7.5 (HIGH)
Affected Versions before 0.37.1
Fixed In 0.37.1
Type CWE-248 (Uncaught Exception)
Vendor Yhirose
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service

CVSS Vector v3.1

Weakness Type (CWE)

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Yhirose Cpp-Httplib
cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*
0.37.1