Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh (CVE-2026-39831) | HOL Guard CVE

Critical · CVSS 9.1CVE-2026-39831GHSA-89GR-R52H-F8RX

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

Answer in brief

CVE-2026-39831 records a Critical severity (CVSS 9.1) vulnerability in Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh. The current sources do not mark it as known exploited. The current feed maps golang.org/x/crypto (go), golang.org/x/crypto (go), golang.org/x/crypto/ssh (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published May 22, 2026Updated Sep 15, 2026Source checked Sep 15, 2026First seen by HOL Jun 25, 2026Material review Sep 15, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.1
Exploitation: Not marked as known exploited
Affected software: 3 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 9.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps golang.org/x/crypto (go), golang.org/x/crypto (go), golang.org/x/crypto/ssh (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
golang.org/x/cryptogo	<0.52.0	0.52.0
golang.org/x/cryptogo	>=0 <0.52.0	0.52.0
golang.org/x/crypto/sshgo	<0.52.0	0.52.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for golang.org/x/crypto, golang.org/x/crypto, golang.org/x/crypto/ssh.
Review the reported fix. Update golang.org/x/crypto to 0.52.0; golang.org/x/crypto to 0.52.0; golang.org/x/crypto/ssh to 0.52.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
May 22, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 15, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Jun 25, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.