CRLF injection in Cpp-httplib - CVE-2026-21428
Published: January 5, 2026
Vulnerability identifier: #VU120925
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2026-21428
CWE-ID: CWE-93
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Cpp-httplib Project
Affected software:
Cpp-httplib
Cpp-httplib
Detailed vulnerability description
The vulnerability allows a remote attacker to inject arbitrary HTTP headers.
The vulnerability exists due to insufficient validation of attacker-supplied data. A remote attacker can send a specially crafted HTTP request to the application containing CR-LF characters and modify application behavior. When combined with a server that supports http1.1 pipelining this can be used for server side request forgery attacks.
How to mitigate CVE-2026-21428
Install updates from vendor's website.