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CVE-2026-39831

41
FAUCET Score

The Verify() method for FIDO/U2F security key types ([email protected], [email protected]) 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.

First published: May 22, 2026Last modified: May 22, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 0.52.0CPE matchmatch criteria
cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:*

CVSS Data

CVSS version used by this source: 3.1

9.1CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.42%
Probability of exploitation in next 30 days
EPSS Percentile
34.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0042 is in the 11th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

gopatch availablevia ghsa
Product: golang.org/x/cryptoFixed in: 0.52.0

Vendor Advisories (2)

goGHSA-89gr-r52h-f8rxcritical

golang.org/x/crypto: FIDO/U2F security key physical presence check can be bypassed

Jun 25, 2026
microsoft2026-May/CVE-2026-39831Important

Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh

May 12, 2026

References

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