FKIE_CVE-2026-42505

Vulnerability from fkie_nvd - Published: 2026-07-08 17:17 - Updated: 2026-07-13 17:05
Severity
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Summary
Handshakes which used Encrypted Client Hello could be de-anonymized by a passive network observer due to a disclosure of pre-shared key identities in the unencrypted client hello.
References
security@golang.orghttps://go.dev/cl/775960Patch
security@golang.orghttps://go.dev/issue/79282Issue Tracking, Patch
security@golang.orghttps://groups.google.com/g/golang-announce/c/OrmQE_Yp5ScMailing List, Release Notes, Vendor Advisory
security@golang.orghttps://pkg.go.dev/vuln/GO-2026-5856Vendor Advisory
Impacted products
Vendor Product Version
golang go *
golang go *
golang go 1.27
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "crypto/tls",
          "product": "crypto/tls",
          "programRoutines": [
            {
              "name": "clientHelloMsg.marshalMsg"
            },
            {
              "name": "Conn.Handshake"
            },
            {
              "name": "Conn.HandshakeContext"
            },
            {
              "name": "Conn.Read"
            },
            {
              "name": "Conn.Write"
            },
            {
              "name": "Dial"
            },
            {
              "name": "DialWithDialer"
            },
            {
              "name": "Dialer.Dial"
            },
            {
              "name": "Dialer.DialContext"
            },
            {
              "name": "QUICConn.HandleData"
            },
            {
              "name": "QUICConn.SendSessionTicket"
            },
            {
              "name": "QUICConn.Start"
            }
          ],
          "vendor": "Go standard library",
          "versions": [
            {
              "lessThan": "1.25.12",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.26.5",
              "status": "affected",
              "version": "1.26.0-0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.27.0-rc.2",
              "status": "affected",
              "version": "1.27.0-0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "security@golang.org"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "BA474C81-2BDB-451D-BAC7-5714B4F30E1F",
              "versionEndExcluding": "1.25.12",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "08CDCAED-0C22-42D9-97A8-77F19DEECDB2",
              "versionEndExcluding": "1.26.5",
              "versionStartIncluding": "1.26.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:golang:go:1.27:rc1:*:*:*:*:*:*",
              "matchCriteriaId": "1062DCC7-46FE-4CF5-ADEF-BEC03F8AB39E",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Handshakes which used Encrypted Client Hello could be de-anonymized by a passive network observer due to a disclosure of pre-shared key identities in the unencrypted client hello."
    }
  ],
  "id": "CVE-2026-42505",
  "lastModified": "2026-07-13T17:05:36.303",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-42505",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-08T18:03:53.821942Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-08T17:17:21.497",
  "references": [
    {
      "source": "security@golang.org",
      "tags": [
        "Patch"
      ],
      "url": "https://go.dev/cl/775960"
    },
    {
      "source": "security@golang.org",
      "tags": [
        "Issue Tracking",
        "Patch"
      ],
      "url": "https://go.dev/issue/79282"
    },
    {
      "source": "security@golang.org",
      "tags": [
        "Mailing List",
        "Release Notes",
        "Vendor Advisory"
      ],
      "url": "https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc"
    },
    {
      "source": "security@golang.org",
      "tags": [
        "Vendor Advisory"
      ],
      "url": "https://pkg.go.dev/vuln/GO-2026-5856"
    }
  ],
  "sourceIdentifier": "security@golang.org",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-201"
        }
      ],
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "type": "Secondary"
    }
  ]
}



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Sightings

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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.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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