Vulnerability-Lookup

FKIE_CVE-2026-39831

Vulnerability from fkie_nvd - Published: 2026-05-22 04:16 - Updated: 2026-05-22 04:16

Severity

Summary

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.

References

	URL	Tags
	security@golang.org	https://go.dev/cl/781662
	security@golang.org	https://go.dev/issue/79566
	security@golang.org	https://groups.google.com/g/golang-announce/c/a082jnz-LvI
	security@golang.org	https://pkg.go.dev/vuln/GO-2026-5019

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    }
  ],
  "id": "CVE-2026-39831",
  "lastModified": "2026-05-22T04:16:22.553",
  "metrics": {},
  "published": "2026-05-22T04:16:22.553",
  "references": [
    {
      "source": "security@golang.org",
      "url": "https://go.dev/cl/781662"
    },
    {
      "source": "security@golang.org",
      "url": "https://go.dev/issue/79566"
    },
    {
      "source": "security@golang.org",
      "url": "https://groups.google.com/g/golang-announce/c/a082jnz-LvI"
    },
    {
      "source": "security@golang.org",
      "url": "https://pkg.go.dev/vuln/GO-2026-5019"
    }
  ],
  "sourceIdentifier": "security@golang.org",
  "vulnStatus": "Received"
}

CVE-2026-39831 (GCVE-0-2026-39831)

Vulnerability from cvelistv5 – Published: 2026-05-22 02:31 – Updated: 2026-05-22 18:52

Title

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

Summary

Severity

9.1 (Critical)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CWE

CWE-290 - Authentication Bypass by Spoofing

Assigner

References

4 references

URL	Tags
https://go.dev/issue/79566
https://groups.google.com/g/golang-announce/c/a08…
https://go.dev/cl/781662
https://pkg.go.dev/vuln/GO-2026-5019

Impacted products

1 product

Vendor	Product	Version
golang.org/x/crypto	golang.org/x/crypto/ssh	Affected: 0 , < 0.52.0 (semver)

Credits

NCC Group Cryptography Services, sponsored by Teleport

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 9.1,
              "baseSeverity": "CRITICAL",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-39831",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-22T18:51:41.233749Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-22T18:52:08.344Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "golang.org/x/crypto/ssh",
          "product": "golang.org/x/crypto/ssh",
          "programRoutines": [
            {
              "name": "CertChecker.CheckCert"
            },
            {
              "name": "skECDSAPublicKey.Verify"
            },
            {
              "name": "skEd25519PublicKey.Verify"
            },
            {
              "name": "connection.serverAuthenticate"
            },
            {
              "name": "CertChecker.Authenticate"
            },
            {
              "name": "CertChecker.CheckHostKey"
            },
            {
              "name": "Certificate.Verify"
            },
            {
              "name": "Dial"
            },
            {
              "name": "NewClientConn"
            },
            {
              "name": "NewServerConn"
            }
          ],
          "vendor": "golang.org/x/crypto",
          "versions": [
            {
              "lessThan": "0.52.0",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "NCC Group Cryptography Services, sponsored by Teleport"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-290: Authentication Bypass by Spoofing",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-22T02:31:27.436Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/issue/79566"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/a082jnz-LvI"
        },
        {
          "url": "https://go.dev/cl/781662"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-5019"
        }
      ],
      "title": "Invoking  bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-39831",
    "datePublished": "2026-05-22T02:31:27.436Z",
    "dateReserved": "2026-04-07T18:13:03.528Z",
    "dateUpdated": "2026-05-22T18:52:08.344Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

FKIE_CVE-2026-39831

CVE-2026-39831 (GCVE-0-2026-39831)

Tags

Sightings

Nomenclature