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CVE-2026-39831 Critical

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

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.

Exploit probability 0.4%
Published May 22, 2026
Required by Not available
Last source change June 25, 2026

02 / AFFECTED SOFTWARE

Affected packages

Go golang.org/x/crypto
Go golang.org/x/crypto
Unknown Unknown

51 explicit affected versions

03 / CONNECTIONS

Connected vulnerabilities

related OPENSUSE-SU-2026:21483-1

04 / EVIDENCE

Source records

Open Source Vulnerabilities CVE-2026-39831

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.

View original source
Open Source Vulnerabilities GHSA-89gr-r52h-f8rx

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.

View original source
Open Source Vulnerabilities GO-2026-5019

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.

View original source

05 / REFERENCES

Further evidence