CVE-2026-45372 — cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection

Affected: yhirose cpp-httplib

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The validity check (is_field_value) is run before decoding, so encoded %0D%0A passes the check and is then expanded to a literal \r\n byte pair inside the stored header value. This vulnerability is fixed in 0.44.0.

USN-8470-1 — cpp-httplib vulnerability

Affected: Ubuntu:Pro:22.04:LTS: cpp-httplib, Ubuntu:Pro:24.04:LTS: cpp-httplib, Ubuntu:25.10: cpp-httplib, Ubuntu:Pro:26.04:LTS: cpp-httplib

It was discovered that cpp-httplib incorrectly percent-decoded HTTP request header values. A remote attacker could use this to inject crafted header content possibly leading to response splitting, log injection or proxy smuggling.

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CVE-2026-45372 — cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection

USN-8470-1 — cpp-httplib vulnerability