CVE-2026-45372CWE-444CWE-93
cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection
Critical · published May 29, 2026
What it is
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.
The record
Technical detail
- CVSS v3.1
- 9.9 · CRITICAL
- Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L
- CVSS v4.0
- Not supplied
- EPSS
- 0.00410 · 34.1th percentile
- Weaknesses
- CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling'); CWE-93 · Improper Neutralization of CRLF Sequences ('CRLF Injection')
- Published
- 2026-05-29T19:21Z
EPSS history
Timeline