{"id":"CVE-2026-39831","aliases":["GHSA-89gr-r52h-f8rx","GO-2026-5019"],"url":"https://o3.security/vulnerability/CVE-2026-39831","summary":"Invoking  bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh","details":"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.","published":"2026-05-22T02:31:27.436Z","modified":"2026-08-27T17:40:58.116280060Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":{"score":0.0042,"percentile":0.35233,"asOf":"2026-09-06"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"golang.org/x/crypto","fixedVersion":"0.52.0"}],"fix":null,"references":[{"type":"WEB","url":"https://go.dev/cl/781662"},{"type":"WEB","url":"https://go.dev/issue/79566"},{"type":"WEB","url":"https://groups.google.com/g/golang-announce/c/a082jnz-LvI"},{"type":"WEB","url":"https://pkg.go.dev"},{"type":"WEB","url":"https://pkg.go.dev/vuln/GO-2026-5019"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39831.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39831"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-27T17:40:58.116280060Z"}}