How severe is CVE-2026-45372?

CVE-2026-45372 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability low.

Is CVE-2026-45372 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-45372?

CVE-2026-45372 affects Yhirose Cpp-httplib. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-45372?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-45372 have an EU (EUVD) identifier?

Yes. CVE-2026-45372 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33427.

When was CVE-2026-45372 published?

CVE-2026-45372 was published on 2026-05-29 and last updated on 2026-07-22.

CVE-2026-45372

CVE-2026-45372 is a critical-severity vulnerability in Yhirose Cpp-httplib with a CVSS 3.x base score of 9.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-93.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
EPSS exploit prediction: 0% (33rd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-33427
Weakness: CWE-93
Affected product: Yhirose Cpp-httplib
Published: 2026-05-29
Last 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.

Frequently asked questions

What is CVE-2026-45372?: 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.
How severe is CVE-2026-45372?: CVE-2026-45372 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity high, and availability low.
Is CVE-2026-45372 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-45372?: CVE-2026-45372 affects Yhirose Cpp-httplib. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-45372?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-45372 have an EU (EUVD) identifier?: Yes. CVE-2026-45372 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33427.
When was CVE-2026-45372 published?: CVE-2026-45372 was published on 2026-05-29 and last updated on 2026-07-22.

References

https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-xjxg-64p4-vj4m

Affected products (1)

cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*

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