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.
Published: 2026-05-29
Score: 9.9 Critical
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Ubuntu USN Ubuntu USN USN-8470-1 cpp-httplib vulnerability
History

Mon, 01 Jun 2026 18:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*

Mon, 01 Jun 2026 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 29 May 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Yhirose
Yhirose cpp-httplib
Vendors & Products Yhirose
Yhirose cpp-httplib

Fri, 29 May 2026 20:15:00 +0000

Type Values Removed Values Added
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.
Title cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection
Weaknesses CWE-444
CWE-93
References
Metrics cvssV3_1

{'score': 9.9, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L'}


Subscriptions

Yhirose Cpp-httplib
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-06-01T17:57:44.116Z

Reserved: 2026-05-12T00:51:29.086Z

Link: CVE-2026-45372

cve-icon Vulnrichment

Updated: 2026-06-01T17:57:06.726Z

cve-icon NVD

Status : Modified

Published: 2026-05-29T20:16:26.473

Modified: 2026-06-01T19:16:51.283

Link: CVE-2026-45372

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-29T21:30:06Z

Weaknesses