The cpp-httplib C++ HTTP/HTTPS client library versions before 0.39.0 improperly forward stored authentication credentials in the Authorization header to arbitrary hosts when following cross-origin HTTP redirects (status codes 301, 302, 307, 308). This behavior can be exploited by a malicious or compromised server to redirect the client to an attacker-controlled host, thereby exposing sensitive credentials in plaintext. The vulnerability is classified as CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) and has a CVSS 3.1 base score of 7.4, indicating high severity. The issue is resolved in version 0.39.0 of cpp-httplib.

An attacker controlling or compromising a server that the client connects to can cause the client to follow a redirect to a malicious host and leak sensitive authentication credentials (Basic Auth, Bearer Token, Digest Auth) in plaintext. This exposure can lead to unauthorized access to protected resources or services that rely on these credentials. There are no known exploits in the wild at this time.

Upgrade to cpp-httplib version 0.39.0 or later, where this vulnerability is fixed. No other mitigations are indicated by the vendor advisory. Patch status is confirmed by the version update information.