CVE-2026-21428

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 v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://github.com/yhirose/cpp-httplib/commit/98048a033a532ff22320ce1d11789f8d5710dfcd	Patch
https://github.com/yhirose/cpp-httplib/releases/tag/v0.30.0	Product Release Notes
https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7	Exploit Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*

History

06 Jan 2026, 18:20

Type	Values Removed	Values Added
CVSS	v2 : ~~unknown~~ v3 : ~~unknown~~	v2 : unknown v3 : 7.5
CPE		cpe:2.3:a:yhirose:cpp-httplib::::::::
First Time		Yhirose cpp-httplib Yhirose
References	~~() https://github.com/yhirose/cpp-httplib/commit/98048a033a532ff22320ce1d11789f8d5710dfcd -~~	() https://github.com/yhirose/cpp-httplib/commit/98048a033a532ff22320ce1d11789f8d5710dfcd - Patch
References	~~() https://github.com/yhirose/cpp-httplib/releases/tag/v0.30.0 -~~	() https://github.com/yhirose/cpp-httplib/releases/tag/v0.30.0 - Product, Release Notes
References	~~() https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7 -~~	() https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-wpc6-j37r-jcx7 - Exploit, Third Party Advisory

01 Jan 2026, 18:15

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-01-01 18:15

Updated : 2026-01-06 18:20

NVD link : CVE-2026-21428

Mitre link : CVE-2026-21428

CVE.ORG link : CVE-2026-21428

JSON object : View

Products Affected

yhirose

cpp-httplib

CWE

CWE-93

Improper Neutralization of CRLF Sequences ('CRLF Injection')

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