yhirose cpp-httplib up to 0.34.x set_exception_handler information disclosure

Summaryinfo

A vulnerability has been found in yhirose cpp-httplib up to 0.34.x and classified as problematic. Affected by this issue is the function set_exception_handler. Performing a manipulation results in information disclosure. This vulnerability is known as CVE-2026-28434. Remote exploitation of the attack is possible. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in yhirose cpp-httplib up to 0.34.x. It has been classified as problematic. This affects the function set_exception_handler. The manipulation with an unknown input leads to a information disclosure vulnerability. CWE is classifying the issue as CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. This is going to have an impact on confidentiality. The summary by CVE is:

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.35.0, when a request handler throws a C++ exception and the application has not registered a custom exception handler via set_exception_handler(), the library catches the exception and writes its message directly into the HTTP response as a header named EXCEPTION_WHAT. This header is sent to whoever made the request, with no authentication check and no special configuration required to trigger it. The behavior is on by default. A developer who does not know to opt in to set_exception_handler() will ship a server that leaks internal exception messages to any client. This vulnerability is fixed in 0.35.0.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-28434 since 02/27/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 301041 (Linux Distros Unpatched Vulnerability : CVE-2026-28434), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 0.35.0 eliminates this vulnerability. Applying the patch defd907c7469c5c8281247b73bbd07be24c31164 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (301041). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• yhirose

Name

• cpp-httplib

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21
• 0.22
• 0.23
• 0.24
• 0.25
• 0.26
• 0.27
• 0.28
• 0.29
• 0.30
• 0.31
• 0.32
• 0.33
• 0.34

License

• open-source

Website

• Product: https://github.com/yhirose/cpp-httplib/

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