CVE-2026-45372
cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection
Vexday Risk Score
28Low
SSVC decision (CISA)
Track
No exploitation signal → monitor
CVSS 9.9EPSS 0.3%KEV nãoPoC —Nuclei —Metasploit —Patch —
Lifecycle
29 May 2026Published on NVD
Recommendation: Monitor — no exploitation signal at the moment.
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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L
Affected products
yhirose · cpp-httplibWant to know if your infrastructure is exposed to this?
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