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CVE-2026-21428

7.5 · HIGH

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library.

Published Jan 1, 2026CWE-93EPSS 0.41%

Overview

CVE-2026-21428 is a high-severity vulnerability. It was published on January 1, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.30.0, the ``write_headers`` function does not check for CR & LF characters in user supplied headers, allowing untrusted header value to escape header lines.

This vulnerability allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack. When combined with a server that supports http1.1 pipelining (springboot, python twisted etc), this can be used for server side request forgery (SSRF). Version 0.30.0 fixes this issue.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/yhirose/cpp-httplib/commit/98048a033a532ff22320ce1d11789f8d5710dfcdGitHubgithub.com/yhirose/cpp-httplib/releases/tag/v0.30.0GitHubgithub.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7

How CyberStrike helps

Frequently asked questions

What is CVE-2026-21428?

CVE-2026-21428 is a high-severity vulnerability. It was published on January 1, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-21428?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-21428?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-21428?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-21428 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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