by Kastro
Paper/Archive/CVE-2026-45372

CVE-2026-45372

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

EPSS 0.3%public exploitCVSS 9.9
critical.is priorityof 100
44
CVSS 9.9 (CNA)9.9 / 10 × 3029.7Not in CISA KEV+300.0EPSS percentile 22.1.221 × 204.4Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
cpp-httplib< 0.44.0–CNA

Scores by source

GitHub_M (CNA)9.9CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: partial

References

exploitgithub.com/yhirose/cpp-httplib/security/advisories/GHSA-xjxg-64p4-vj4m