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

Vulnerability from cvelistv5 – Published: 2026-05-22 02:31 – Updated: 2026-05-22 18:52
VLAI
Title
Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh
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.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-290 - Authentication Bypass by Spoofing
Assigner
Go
References
Impacted products
Vendor Product Version
golang.org/x/crypto golang.org/x/crypto/ssh Affected: 0 , < 0.52.0 (semver)
Create a notification for this product.
Credits
NCC Group Cryptography Services, sponsored by Teleport
Show details on NVD website
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",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-39831",
      "date": "2026-08-01",
      "epss": "0.0042",
      "percentile": "0.34626"
    },
    "microsoft_vex": {
      "current_release_date": "2026-06-02T14:39:43.000Z",
      "cve": "CVE-2026-39831",
      "id": "msrc_CVE-2026-39831",
      "initial_release_date": "2026-05-02T00:00:00.000Z",
      "product_status:known_not_affected": "12",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Invoking  bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-39831.json",
      "version": "3"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-39831\",\"sourceIdentifier\":\"security@golang.org\",\"published\":\"2026-05-22T04:16:22.553\",\"lastModified\":\"2026-07-23T16:10:00.137\",\"vulnStatus\":\"Analyzed\",\"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.\"},{\"lang\":\"es\",\"value\":\"El m\u00e9todo Verify() para tipos de clave de seguridad FIDO/U2F (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) no verificaba el indicador de Presencia de Usuario. Se aceptaban firmas generadas sin contacto f\u00edsico, lo que permit\u00eda el uso desatendido de una clave de seguridad de hardware. Para restaurar el comportamiento anterior, devuelva una extensi\u00f3n \u0027no-touch-required\u0027 en Permissions.Extensions desde PublicKeyCallback.\"}],\"affected\":[{\"source\":\"security@golang.org\",\"affectedData\":[{\"vendor\":\"golang.org/x/crypto\",\"product\":\"golang.org/x/crypto/ssh\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://pkg.go.dev\",\"packageName\":\"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\"}],\"versions\":[{\"version\":\"0\",\"lessThan\":\"0.52.0\",\"versionType\":\"semver\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N\",\"baseScore\":9.1,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":5.2}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-05-22T18:51:41.233749Z\",\"id\":\"CVE-2026-39831\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-862\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:*\",\"versionEndExcluding\":\"0.52.0\",\"matchCriteriaId\":\"D540395B-31B8-4B07-8F79-F5C631BBD5C8\"}]}]}],\"references\":[{\"url\":\"https://go.dev/cl/781662\",\"source\":\"security@golang.org\",\"tags\":[\"Issue Tracking\"]},{\"url\":\"https://go.dev/issue/79566\",\"source\":\"security@golang.org\",\"tags\":[\"Issue Tracking\"]},{\"url\":\"https://groups.google.com/g/golang-announce/c/a082jnz-LvI\",\"source\":\"security@golang.org\",\"tags\":[\"Mailing List\"]},{\"url\":\"https://pkg.go.dev/vuln/GO-2026-5019\",\"source\":\"security@golang.org\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-07-31T15:09:55+00:00",
      "cve": "CVE-2026-39831",
      "id": "CVE-2026-39831",
      "initial_release_date": "2026-05-22T02:31:27.436000+00:00",
      "product_status:fixed": "154",
      "product_status:known_affected": "210",
      "product_status:known_not_affected": "291",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "golang.org/x/crypto/ssh: golang.org/x/crypto/ssh: Security key bypass due to missing user presence check",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39831.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-07-21T13:13:42Z",
      "cve": "CVE-2026-39831",
      "id": "CVE-2026-39831",
      "initial_release_date": "2026-05-23T01:29:07Z",
      "product_status:first_fixed": "8",
      "product_status:known_affected": "387",
      "product_status:known_not_affected": "254",
      "product_status:recommended": "363",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-39831",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-39831.json",
      "version": "34"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 9.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"CRITICAL\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"HIGH\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-39831\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-22T18:51:41.233749Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-22T18:51:54.995Z\"}}], \"cna\": {\"title\": \"Invoking  bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh\", \"credits\": [{\"lang\": \"en\", \"value\": \"NCC Group Cryptography Services, sponsored by Teleport\"}], \"affected\": [{\"vendor\": \"golang.org/x/crypto\", \"product\": \"golang.org/x/crypto/ssh\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"0.52.0\", \"versionType\": \"semver\"}], \"packageName\": \"golang.org/x/crypto/ssh\", \"collectionURL\": \"https://pkg.go.dev\", \"defaultStatus\": \"unaffected\", \"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\"}]}], \"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\"}], \"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\": [{\"lang\": \"en\", \"description\": \"CWE-290: Authentication Bypass by Spoofing\"}]}], \"providerMetadata\": {\"orgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"shortName\": \"Go\", \"dateUpdated\": \"2026-05-22T02:31:27.436Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-39831\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-22T18:52:08.344Z\", \"dateReserved\": \"2026-04-07T18:13:03.528Z\", \"assignerOrgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"datePublished\": \"2026-05-22T02:31:27.436Z\", \"assignerShortName\": \"Go\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.