CVE-2026-39831

Name: CVE-2026-39831
Creator: NVD / NIST
Published: 2026-05-22T04:16:22.553+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.1/10EPSS 0.37%

Last modified Jun 17, 2026

CVE-2026-39831 is a critical-severity vulnerability rated 9.1/10 on the CVSS scale. The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. EPSS estimates a 0.37% chance of exploitation in the next 30 days.

Description

The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.

Metrics

CVSS 3.1

9.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Probability

0.37%

29.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-862

Affected Software

Vendor	Product	Versions
Golang	Crypto	< 0.52.0

References

https://go.dev/cl/781662Issue Tracking
https://go.dev/issue/79566Issue Tracking
https://groups.google.com/g/golang-announce/c/a082jnz-LvIMailing List
https://pkg.go.dev/vuln/GO-2026-5019Vendor Advisory

Timeline

Published: May 22, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-39831?

How severe is CVE-2026-39831?

CVE-2026-39831 has a CVSS score of 9.1/10 (CRITICAL severity). The EPSS model estimates a 0.37% probability of exploitation in the next 30 days.

How do I fix CVE-2026-39831?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-39831?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST