What is CVE-2025-66570?

CVE-2025-66570 is a critical-severity vulnerability in Yhirose Cpp-httplib, classified under Authentication Bypass by Spoofing. CVSS score: 10.0/10. Published 2025-12-05.

How severe is CVE-2025-66570?

Critical severity. CVSS v3 base score is 10.0 out of 10.

Vulnerability in Yhirose Cpp-httplib

CVE-2025-66570

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.27.0, a vulnerability allows attacker-controlled HTTP headers to influence server-visible metadata, logging, and authorization decisions. An attac…

EPSS: 0.000 (9.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 10.0 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N.

Affected products

Yhirose Cpp-httplib — versions < 0.27.0

Weakness classification (CWE)

References

https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-xm2j-vfr9-mg9m (x_refsource_CONFIRM)
https://github.com/yhirose/cpp-httplib/commit/ac9ebb0ee333ce8bf13523f487bdfad9518a2aff (x_refsource_MISC)

Frequently asked questions

What is CVE-2025-66570?: CVE-2025-66570 is a critical-severity vulnerability in Yhirose Cpp-httplib, classified under Authentication Bypass by Spoofing. CVSS score: 10.0/10. Published 2025-12-05.
How severe is CVE-2025-66570?: Critical severity. CVSS v3 base score is 10.0 out of 10.