CVE-2026-39831
Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.42%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 0.42% probability · 36th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-862
- Affected
- golang/crypto
- Source
- security@golang.org
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
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.