CVE-2026-21428
cpp-httplib has CRLF injection in http headers
- State
- Published
- Severity
- 7.7 High
- Published
- Jan 1, 2026
- Updated
- Jan 2, 2026
- Reserved
- Dec 29, 2025
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 7.7 High | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P | GitHub_M |
Weaknesses
- CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
Affected Products
| Product | Versions |
|---|---|
cpp-httplibyhirose |
|
References
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