CVE-2026-39826 (GCVE-0-2026-39826)

Vulnerability from cvelistv5 – Published: 2026-05-07 19:41 – Updated: 2026-05-08 14:05
VLAI
Title
Escaper bypass leads to XSS in html/template
Summary
If a trusted template author were to write a <script> tag containing an empty 'type' attribute or a 'type' attribute with an ASCII whitespace, the execution of the template would incorrectly escape any data passed into the <script> block.
Severity
6.1 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-08 14:04 UTC
CWE
  • CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Assigner
References
Impacted products
Vendor Product Version CPE status
Go standard library html/template Affected: 0 , < 1.25.10 (semver)
Affected: 1.26.0-0 , < 1.26.3 (semver)
guessed Create a notification for this product.
Credits
Mundur (https://github.com/M0nd0R)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "NONE",
              "baseScore": 6.1,
              "baseSeverity": "MEDIUM",
              "confidentialityImpact": "LOW",
              "integrityImpact": "LOW",
              "privilegesRequired": "NONE",
              "scope": "CHANGED",
              "userInteraction": "REQUIRED",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-39826",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-08T14:04:40.842823Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-08T14:05:05.849Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "html/template",
          "product": "html/template",
          "programRoutines": [
            {
              "name": "isJSType"
            },
            {
              "name": "Template.Execute"
            },
            {
              "name": "Template.ExecuteTemplate"
            }
          ],
          "vendor": "Go standard library",
          "versions": [
            {
              "lessThan": "1.25.10",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.26.3",
              "status": "affected",
              "version": "1.26.0-0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Mundur (https://github.com/M0nd0R)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "If a trusted template author were to write a \u003cscript\u003e tag containing an empty \u0027type\u0027 attribute or a \u0027type\u0027 attribute with an ASCII whitespace, the execution of the template would incorrectly escape any data passed into the \u003cscript\u003e block."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-07T19:41:19.138Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/issue/78981"
        },
        {
          "url": "https://go.dev/cl/771180"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/qcCIEXso47M"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-4980"
        }
      ],
      "title": "Escaper bypass leads to XSS in html/template"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-39826",
    "datePublished": "2026-05-07T19:41:19.138Z",
    "dateReserved": "2026-04-07T18:13:03.528Z",
    "dateUpdated": "2026-05-08T14:05:05.849Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-39826",
      "date": "2026-08-25",
      "epss": "0.00371",
      "percentile": "0.29851"
    },
    "microsoft_vex": {
      "current_release_date": "2026-06-23T14:46:00.000Z",
      "cve": "CVE-2026-39826",
      "id": "msrc_CVE-2026-39826",
      "initial_release_date": "2026-05-02T00:00:00.000Z",
      "product_status:known_affected": "2",
      "product_status:known_not_affected": "5",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Escaper bypass leads to XSS in html/template",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-39826.json",
      "version": "6"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-39826\",\"sourceIdentifier\":\"security@golang.org\",\"published\":\"2026-05-07T20:16:43.490\",\"lastModified\":\"2026-06-17T10:42:38.923\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"If a trusted template author were to write a \u003cscript\u003e tag containing an empty \u0027type\u0027 attribute or a \u0027type\u0027 attribute with an ASCII whitespace, the execution of the template would incorrectly escape any data passed into the \u003cscript\u003e block.\"}],\"affected\":[{\"source\":\"security@golang.org\",\"affectedData\":[{\"vendor\":\"Go standard library\",\"product\":\"html/template\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://pkg.go.dev\",\"packageName\":\"html/template\",\"programRoutines\":[{\"name\":\"isJSType\"},{\"name\":\"Template.Execute\"},{\"name\":\"Template.ExecuteTemplate\"}],\"versions\":[{\"version\":\"0\",\"lessThan\":\"1.25.10\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"1.26.0-0\",\"lessThan\":\"1.26.3\",\"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:R/S:C/C:L/I:L/A:N\",\"baseScore\":6.1,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"REQUIRED\",\"scope\":\"CHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":2.8,\"impactScore\":2.7}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-05-08T14:04:40.842823Z\",\"id\":\"CVE-2026-39826\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-116\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"1.25.10\",\"matchCriteriaId\":\"1C966EF3-C51C-4239-B5FC-C44A5202FEC8\"},{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"1.26.0\",\"versionEndExcluding\":\"1.26.3\",\"matchCriteriaId\":\"522E4CD0-2B99-4363-9C78-0BAFD988A2D6\"}]}]}],\"references\":[{\"url\":\"https://go.dev/cl/771180\",\"source\":\"security@golang.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://go.dev/issue/78981\",\"source\":\"security@golang.org\",\"tags\":[\"Patch\"]},{\"url\":\"https://groups.google.com/g/golang-announce/c/qcCIEXso47M\",\"source\":\"security@golang.org\",\"tags\":[\"Release Notes\"]},{\"url\":\"https://pkg.go.dev/vuln/GO-2026-4980\",\"source\":\"security@golang.org\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-25T20:47:38+00:00",
      "cve": "CVE-2026-39826",
      "id": "CVE-2026-39826",
      "initial_release_date": "2026-05-07T19:41:19.138000+00:00",
      "product_status:fixed": "156",
      "product_status:known_affected": "334",
      "product_status:known_not_affected": "186",
      "product_status:under_investigation": "14",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "html/template: golang: html/template: Cross-site scripting due to incorrect script tag escaping",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39826.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"CHANGED\", \"version\": \"3.1\", \"baseScore\": 6.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N\", \"integrityImpact\": \"LOW\", \"userInteraction\": \"REQUIRED\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"NONE\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"LOW\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-39826\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-08T14:04:40.842823Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-08T14:05:00.652Z\"}}], \"cna\": {\"title\": \"Escaper bypass leads to XSS in html/template\", \"credits\": [{\"lang\": \"en\", \"value\": \"Mundur (https://github.com/M0nd0R)\"}], \"affected\": [{\"vendor\": \"Go standard library\", \"product\": \"html/template\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"1.25.10\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"1.26.0-0\", \"lessThan\": \"1.26.3\", \"versionType\": \"semver\"}], \"packageName\": \"html/template\", \"collectionURL\": \"https://pkg.go.dev\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"isJSType\"}, {\"name\": \"Template.Execute\"}, {\"name\": \"Template.ExecuteTemplate\"}]}], \"references\": [{\"url\": \"https://go.dev/issue/78981\"}, {\"url\": \"https://go.dev/cl/771180\"}, {\"url\": \"https://groups.google.com/g/golang-announce/c/qcCIEXso47M\"}, {\"url\": \"https://pkg.go.dev/vuln/GO-2026-4980\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"If a trusted template author were to write a \u003cscript\u003e tag containing an empty \u0027type\u0027 attribute or a \u0027type\u0027 attribute with an ASCII whitespace, the execution of the template would incorrectly escape any data passed into the \u003cscript\u003e block.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"description\": \"CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"shortName\": \"Go\", \"dateUpdated\": \"2026-05-07T19:41:19.138Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-39826\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-08T14:05:05.849Z\", \"dateReserved\": \"2026-04-07T18:13:03.528Z\", \"assignerOrgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"datePublished\": \"2026-05-07T19:41:19.138Z\", \"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.