Critical severity · published May 22, 2026
CVE-2026-39831
Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
9.1
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 41% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
GO
golang.org/x/crypto/ssh · golang.org/x/crypto
before 0.52.0 · source: vendor
CR
Crypto · Golang
before 0.52.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39831
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39831
Issue Tracking
https://go.dev/cl/781662
Issue Tracking
https://go.dev/issue/79566
Mailing List
https://groups.google.com/g/golang-announce/c/a082jnz-LvI
Vendor Advisory
https://pkg.go.dev/vuln/GO-2026-5019
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