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CVE-2026-45372

Yhirose Cpp-httplib vulnerability

9.9 CRITICALPublic exploitEPSS 0.41%
  1. Published29 May 2026

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 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityLow
IntegrityHigh
AvailabilityLow
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:L

Affected products

Yhirose Cpp-httplib< 0.44.0

Remediation

Fixed in
Yhirose Cpp-httplib≥ 0.44.0

References

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Frequently asked

Is CVE-2026-45372 being actively exploited?

CVE-2026-45372 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.41%.

How severe is CVE-2026-45372?

CVE-2026-45372 has a CVSS 3.1 base score of 9.9, rated critical. EPSS estimates a 0.41% probability of exploitation.

Which products are affected by CVE-2026-45372?

Affected products include Yhirose Cpp-httplib.

How do I fix CVE-2026-45372?

Upgrade affected software to a fixed version, for example Yhirose Cpp-httplib 0.44.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-45372 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.