Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Yhirose | Cpp-Httplib | < 0.30.0 |
Related Weaknesses (CWE)
References
- https://github.com/yhirose/cpp-httplib/commit/98048a033a532ff22320ce1d11789f8d57Patch
- https://github.com/yhirose/cpp-httplib/releases/tag/v0.30.0ProductRelease Notes
- https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7ExploitThird Party Advisory
FAQ
What is CVE-2026-21428?
CVE-2026-21428 is a vulnerability with a CVSS score of 7.5 (HIGH). 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...
How severe is CVE-2026-21428?
CVE-2026-21428 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-21428?
Check the references section above for vendor advisories and patch information. Affected products include: Yhirose Cpp-Httplib.