CVE-2026-42505 (GCVE-0-2026-42505)

Vulnerability from cvelistv5 – Published: 2026-07-08 15:46 – Updated: 2026-07-08 19:38
VLAI
Title
Invoking Encrypted Client Hello privacy leak in crypto/tls
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.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-08 18:03 UTC
CWE
  • CWE-201 - Insertion of Sensitive Information Into Sent Data
Assigner
References
Impacted products
Vendor Product Version CPE status
Go standard library crypto/tls Affected: 0 , < 1.25.12 (semver)
Affected: 1.26.0-0 , < 1.26.5 (semver)
Affected: 1.27.0-0 , < 1.27.0-rc.2 (semver)
guessed Create a notification for this product.
Credits
Coia Prant (github.com/rbqvq)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "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"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-42505",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-08T18:03:53.821942Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-201",
                "description": "CWE-201 Insertion of Sensitive Information Into Sent Data",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-08T19:38:17.603Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "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"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Coia Prant (github.com/rbqvq)"
        }
      ],
      "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."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-201: Insertion of Sensitive Information Into Sent Data",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-08T15:46:33.407Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/cl/775960"
        },
        {
          "url": "https://go.dev/issue/79282"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-5856"
        }
      ],
      "title": "Invoking Encrypted Client Hello privacy leak in crypto/tls"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-42505",
    "datePublished": "2026-07-08T15:46:33.407Z",
    "dateReserved": "2026-04-28T00:21:12.792Z",
    "dateUpdated": "2026-07-08T19:38:17.603Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-42505",
      "date": "2026-08-24",
      "epss": "0.00382",
      "percentile": "0.30962"
    },
    "microsoft_vex": {
      "current_release_date": "2026-08-13T00:12:18.000Z",
      "cve": "CVE-2026-42505",
      "id": "msrc_CVE-2026-42505",
      "initial_release_date": "2026-07-15T01:01:45.000Z",
      "product_status:fixed": "1",
      "product_status:known_affected": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Invoking Encrypted Client Hello privacy leak in crypto/tls",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-42505.json",
      "version": "2"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-42505\",\"sourceIdentifier\":\"security@golang.org\",\"published\":\"2026-07-08T17:17:21.497\",\"lastModified\":\"2026-07-13T17:05:36.303\",\"vulnStatus\":\"Analyzed\",\"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.\"}],\"affected\":[{\"source\":\"security@golang.org\",\"affectedData\":[{\"vendor\":\"Go standard library\",\"product\":\"crypto/tls\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://pkg.go.dev\",\"packageName\":\"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\"}],\"versions\":[{\"version\":\"0\",\"lessThan\":\"1.25.12\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"1.26.0-0\",\"lessThan\":\"1.26.5\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"1.27.0-0\",\"lessThan\":\"1.27.0-rc.2\",\"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:L/I:N/A:N\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-07-08T18:03:53.821942Z\",\"id\":\"CVE-2026-42505\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"yes\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-201\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"1.25.12\",\"matchCriteriaId\":\"BA474C81-2BDB-451D-BAC7-5714B4F30E1F\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"1.26.0\",\"versionEndExcluding\":\"1.26.5\",\"matchCriteriaId\":\"08CDCAED-0C22-42D9-97A8-77F19DEECDB2\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:golang:go:1.27:rc1:*:*:*:*:*:*\",\"matchCriteriaId\":\"1062DCC7-46FE-4CF5-ADEF-BEC03F8AB39E\"}]}]}],\"references\":[{\"url\":\"https://go.dev/cl/775960\",\"source\":\"security@golang.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://go.dev/issue/79282\",\"source\":\"security@golang.org\",\"tags\":[\"Issue Tracking\",\"Patch\"]},{\"url\":\"https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc\",\"source\":\"security@golang.org\",\"tags\":[\"Mailing List\",\"Release Notes\",\"Vendor Advisory\"]},{\"url\":\"https://pkg.go.dev/vuln/GO-2026-5856\",\"source\":\"security@golang.org\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-19T00:41:27+00:00",
      "cve": "CVE-2026-42505",
      "id": "CVE-2026-42505",
      "initial_release_date": "2026-07-08T15:46:33.407000+00:00",
      "product_status:fixed": "89",
      "product_status:known_affected": "148",
      "product_status:known_not_affected": "6",
      "product_status:under_investigation": "216",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "crypto/tls: golang: Go crypto/tls: Information disclosure in Encrypted Client Hello",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42505.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 5.3, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"LOW\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-42505\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-07-08T18:03:53.821942Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-201\", \"description\": \"CWE-201 Insertion of Sensitive Information Into Sent Data\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-07-08T18:04:08.858Z\"}}], \"cna\": {\"title\": \"Invoking Encrypted Client Hello privacy leak in crypto/tls\", \"credits\": [{\"lang\": \"en\", \"value\": \"Coia Prant (github.com/rbqvq)\"}], \"affected\": [{\"vendor\": \"Go standard library\", \"product\": \"crypto/tls\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"1.25.12\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"1.26.0-0\", \"lessThan\": \"1.26.5\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"1.27.0-0\", \"lessThan\": \"1.27.0-rc.2\", \"versionType\": \"semver\"}], \"packageName\": \"crypto/tls\", \"collectionURL\": \"https://pkg.go.dev\", \"defaultStatus\": \"unaffected\", \"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\"}]}], \"references\": [{\"url\": \"https://go.dev/cl/775960\"}, {\"url\": \"https://go.dev/issue/79282\"}, {\"url\": \"https://groups.google.com/g/golang-announce/c/OrmQE_Yp5Sc\"}, {\"url\": \"https://pkg.go.dev/vuln/GO-2026-5856\"}], \"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.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"description\": \"CWE-201: Insertion of Sensitive Information Into Sent Data\"}]}], \"providerMetadata\": {\"orgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"shortName\": \"Go\", \"dateUpdated\": \"2026-07-08T15:46:33.407Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-42505\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-08T19:38:17.603Z\", \"dateReserved\": \"2026-04-28T00:21:12.792Z\", \"assignerOrgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"datePublished\": \"2026-07-08T15:46:33.407Z\", \"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.