What is CVE-2026-40947?

CVE-2026-40947 is a low-severity vulnerability in Yubico Libfido2, classified under Untrusted Search Path. CVSS score: 2.9/10. Published 2026-04-16.

How severe is CVE-2026-40947?

Low severity. CVSS v3 base score is 2.9 out of 10.

Vulnerability in Yubico Libfido2

CVE-2026-40947

Yubico libfido2 before 1.17.0, python-fido2 before 2.2.0, and yubikey-manager before 5.9.1 have an unintended DLL search path.

Published 2026-04-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 2.9 (Low). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.001 (2.1th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 2nd percentile — 2.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.001 · newest: 0.001 · change: -0.000

Affected products

Yubico Libfido2 — versions 0
Yubico Python-Fido2 — versions 0
Yubico Yubikey-Manager — versions 0

Weakness classification (CWE)

CWE-426 — Untrusted Search Path

References

www.yubico.com/support/security-advisories/ysa-2026-01/

Frequently asked questions

What is CVE-2026-40947?: CVE-2026-40947 is a low-severity vulnerability in Yubico Libfido2, classified under Untrusted Search Path. CVSS score: 2.9/10. Published 2026-04-16.
How severe is CVE-2026-40947?: Low severity. CVSS v3 base score is 2.9 out of 10.