GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

CVE-2026-56858 (GCVE-0-2026-56858)

Vulnerability from cvelistv5 – Published: 2026-08-13 21:58 – Updated: 2026-08-14 15:32
VLAI
Title
Fix Javascript regexp context tracking in html/template
Summary
Previously, pathological inputs could close an unescaped '/' early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS.
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 2026-08-14 15:31 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 , < 1.25.13 (semver)
Affected: 1.26.0-0 , < 1.26.6 (semver)
Affected: 1.27.0-0 , < 1.27.0-rc.3 (semver)
guessed Create a notification for this product.
Credits
Ali Sherif
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-2026-56858",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-14T15:31:30.140536Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-79",
                "description": "CWE-79 Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-14T15:32:29.852Z",
          "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": "tJS"
            },
            {
              "name": "Template.Execute"
            },
            {
              "name": "Template.ExecuteTemplate"
            }
          ],
          "vendor": "Go standard library",
          "versions": [
            {
              "lessThan": "1.25.13",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.26.6",
              "status": "affected",
              "version": "1.26.0-0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.27.0-rc.3",
              "status": "affected",
              "version": "1.27.0-0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Ali Sherif"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Previously, pathological inputs could close an unescaped \u0027/\u0027 early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-13T21:58:53.354Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/issue/80435"
        },
        {
          "url": "https://go.dev/cl/807100"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/94pEornpRlI"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-6091"
        }
      ],
      "title": "Fix Javascript regexp context tracking in html/template"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-56858",
    "datePublished": "2026-08-13T21:58:53.354Z",
    "dateReserved": "2026-06-23T15:10:49.353Z",
    "dateUpdated": "2026-08-14T15:32:29.852Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-56858",
      "date": "2026-09-16",
      "epss": "0.0031",
      "percentile": "0.23772"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-08T14:49:31.000Z",
      "cve": "CVE-2026-56858",
      "id": "msrc_CVE-2026-56858",
      "initial_release_date": "2026-08-20T22:02:44.000Z",
      "product_status:known_affected": "3",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Fix Javascript regexp context tracking in html/template",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-56858.json",
      "version": "3"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-56858\",\"sourceIdentifier\":\"security@golang.org\",\"published\":\"2026-08-13T22:17:22.207\",\"lastModified\":\"2026-09-03T16:37:52.170\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Previously, pathological inputs could close an unescaped \u0027/\u0027 early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS.\"}],\"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\":\"tJS\"},{\"name\":\"Template.Execute\"},{\"name\":\"Template.ExecuteTemplate\"}],\"versions\":[{\"version\":\"0\",\"lessThan\":\"1.25.13\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"1.26.0-0\",\"lessThan\":\"1.26.6\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"1.27.0-0\",\"lessThan\":\"1.27.0-rc.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\":\"2026-08-14T15:31:30.140536Z\",\"id\":\"CVE-2026-56858\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-79\"}]}],\"references\":[{\"url\":\"https://go.dev/cl/807100\",\"source\":\"security@golang.org\"},{\"url\":\"https://go.dev/issue/80435\",\"source\":\"security@golang.org\"},{\"url\":\"https://groups.google.com/g/golang-announce/c/94pEornpRlI\",\"source\":\"security@golang.org\"},{\"url\":\"https://pkg.go.dev/vuln/GO-2026-6091\",\"source\":\"security@golang.org\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-16T18:14:56+00:00",
      "cve": "CVE-2026-56858",
      "id": "CVE-2026-56858",
      "initial_release_date": "2026-08-13T21:58:53.354000+00:00",
      "product_status:fixed": "1403",
      "product_status:known_affected": "281",
      "product_status:known_not_affected": "529",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "html/template: golang: Go html/template: Cross-Site Scripting via pathological input",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-56858.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-16T00:09:36Z",
      "cve": "CVE-2026-56858",
      "id": "CVE-2026-56858",
      "initial_release_date": "2026-08-14T23:48:57Z",
      "product_status:known_affected": "24",
      "product_status:known_not_affected": "103",
      "product_status:recommended": "353",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-56858",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-56858.json",
      "version": "9"
    },
    "vulnrichment": {
      "containers": "{\"cna\": {\"providerMetadata\": {\"orgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"shortName\": \"Go\", \"dateUpdated\": \"2026-08-13T21:58:53.354Z\"}, \"title\": \"Fix Javascript regexp context tracking in html/template\", \"descriptions\": [{\"lang\": \"en\", \"value\": \"Previously, pathological inputs could close an unescaped \u0027/\u0027 early, allowing for attack-controlled data to inject arbitrary content, potentially leading to XSS.\"}], \"affected\": [{\"vendor\": \"Go standard library\", \"product\": \"html/template\", \"collectionURL\": \"https://pkg.go.dev\", \"packageName\": \"html/template\", \"versions\": [{\"version\": \"0\", \"lessThan\": \"1.25.13\", \"status\": \"affected\", \"versionType\": \"semver\"}, {\"version\": \"1.26.0-0\", \"lessThan\": \"1.26.6\", \"status\": \"affected\", \"versionType\": \"semver\"}, {\"version\": \"1.27.0-0\", \"lessThan\": \"1.27.0-rc.3\", \"status\": \"affected\", \"versionType\": \"semver\"}], \"programRoutines\": [{\"name\": \"tJS\"}, {\"name\": \"Template.Execute\"}, {\"name\": \"Template.ExecuteTemplate\"}], \"defaultStatus\": \"unaffected\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"description\": \"CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}], \"references\": [{\"url\": \"https://go.dev/issue/80435\"}, {\"url\": \"https://go.dev/cl/807100\"}, {\"url\": \"https://groups.google.com/g/golang-announce/c/94pEornpRlI\"}, {\"url\": \"https://pkg.go.dev/vuln/GO-2026-6091\"}], \"credits\": [{\"lang\": \"en\", \"value\": \"Ali Sherif\"}]}, \"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-2026-56858\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-14T15:31:30.140536Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-79\", \"description\": \"CWE-79 Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-14T15:32:20.906Z\"}}]}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-56858\", \"assignerOrgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"state\": \"PUBLISHED\", \"assignerShortName\": \"Go\", \"dateReserved\": \"2026-06-23T15:10:49.353Z\", \"datePublished\": \"2026-08-13T21:58:53.354Z\", \"dateUpdated\": \"2026-08-14T15:32:29.852Z\"}",
      "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.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.