CVE-2026-45372
High
High exploit probability or critical severity with a known exploit.
CVSS base
9.9
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L
EPSS — probability of exploitation (30 days)
0.3%
22.3th percentile
CISA KEV
Not listed
Weakness / dates
CWE-93
Published 2026-05-29 · modified 2026-07-22
Description
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.