Critical severity · published May 29, 2026
CVE-2026-45372
cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection
9.9
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
High
Availability
Low
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 22% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CP
cpp-httplib · yhirose
< 0.44.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-45372
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-45372
Exploit
https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-xjxg-64p4-vj4m
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