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

CVE-2026-42504 (GCVE-0-2026-42504)

Vulnerability from cvelistv5 – Published: 2026-06-02 22:01 – Updated: 2026-09-10 16:34
VLAI
Title
Quadratic complexity in WordDecoder.DecodeHeader in mime
Summary
Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-03 14:05 UTC
CWE
  • CWE-407 - Inefficient Algorithmic Complexity
Assigner
References
Impacted products
Vendor Product Version CPE status
Go standard library mime Affected: 0 , < 1.25.11 (semver)
Affected: 1.26.0-0 , < 1.26.4 (semver)
guessed Create a notification for this product.
Credits
p4p3r (https://hackerone.com/p4p3r_hak)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 7.5,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "NONE",
              "integrityImpact": "NONE",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2026-42504",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-03T14:05:39.682615Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-407",
                "description": "CWE-407 Inefficient Algorithmic Complexity",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-03T14:06:13.623Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "packageName": "mime",
          "product": "mime",
          "programRoutines": [
            {
              "name": "WordDecoder.DecodeHeader"
            }
          ],
          "vendor": "Go standard library",
          "versions": [
            {
              "lessThan": "1.25.11",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThan": "1.26.4",
              "status": "affected",
              "version": "1.26.0-0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "p4p3r (https://hackerone.com/p4p3r_hak)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "CWE-407: Inefficient Algorithmic Complexity",
              "lang": "en"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-10T16:34:26.261Z",
        "orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
        "shortName": "Go"
      },
      "references": [
        {
          "url": "https://go.dev/issue/79217"
        },
        {
          "url": "https://go.dev/cl/774481"
        },
        {
          "url": "https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw"
        },
        {
          "url": "https://pkg.go.dev/vuln/GO-2026-5038"
        }
      ],
      "title": "Quadratic complexity in WordDecoder.DecodeHeader in mime"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
    "assignerShortName": "Go",
    "cveId": "CVE-2026-42504",
    "datePublished": "2026-06-02T22:01:37.219Z",
    "dateReserved": "2026-04-28T00:21:12.792Z",
    "dateUpdated": "2026-09-10T16:34:26.261Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-42504",
      "date": "2026-09-14",
      "epss": "0.0056",
      "percentile": "0.44906"
    },
    "microsoft_vex": {
      "current_release_date": "2026-09-09T15:03:13.000Z",
      "cve": "CVE-2026-42504",
      "id": "msrc_CVE-2026-42504",
      "initial_release_date": "2026-06-05T01:02:08.000Z",
      "product_status:fixed": "3",
      "product_status:known_affected": "6",
      "product_status:known_not_affected": "3",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "Quadratic complexity in WordDecoder.DecodeHeader in mime",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-42504.json",
      "version": "9"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-42504\",\"sourceIdentifier\":\"security@golang.org\",\"published\":\"2026-06-02T23:16:37.927\",\"lastModified\":\"2026-07-22T19:10:00.120\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.\"},{\"lang\":\"es\",\"value\":\"La decodificaci\u00f3n de un encabezado MIME malintencionado que contiene muchas palabras codificadas no v\u00e1lidas puede consumir excesiva CPU.\"}],\"affected\":[{\"source\":\"security@golang.org\",\"affectedData\":[{\"vendor\":\"Go standard library\",\"product\":\"mime\",\"defaultStatus\":\"unaffected\",\"collectionURL\":\"https://pkg.go.dev\",\"packageName\":\"mime\",\"programRoutines\":[{\"name\":\"WordDecoder.DecodeHeader\"}],\"versions\":[{\"version\":\"0\",\"lessThan\":\"1.25.11\",\"versionType\":\"semver\",\"status\":\"affected\"},{\"version\":\"1.26.0-0\",\"lessThan\":\"1.26.4\",\"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:N/I:N/A:H\",\"baseScore\":7.5,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-06-03T14:05:39.682615Z\",\"id\":\"CVE-2026-42504\",\"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-407\"}]}],\"references\":[{\"url\":\"https://go.dev/cl/774481\",\"source\":\"security@golang.org\"},{\"url\":\"https://go.dev/issue/79217\",\"source\":\"security@golang.org\"},{\"url\":\"https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw\",\"source\":\"security@golang.org\"},{\"url\":\"https://pkg.go.dev/vuln/GO-2026-5038\",\"source\":\"security@golang.org\"}]}}",
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-14T05:35:45+00:00",
      "cve": "CVE-2026-42504",
      "id": "CVE-2026-42504",
      "initial_release_date": "2026-06-02T22:01:37.219000+00:00",
      "product_status:fixed": "1027",
      "product_status:known_affected": "145",
      "product_status:known_not_affected": "3709",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "mime: golang: Golang MIME: Denial of Service via maliciously-crafted MIME header",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42504.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}, {\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-42504\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-03T14:05:39.682615Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-407\", \"description\": \"CWE-407 Inefficient Algorithmic Complexity\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-03T14:05:35.965Z\"}}], \"cna\": {\"title\": \"Quadratic complexity in WordDecoder.DecodeHeader in mime\", \"credits\": [{\"lang\": \"en\", \"value\": \"p4p3r (https://hackerone.com/p4p3r_hak)\"}], \"affected\": [{\"vendor\": \"Go standard library\", \"product\": \"mime\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"lessThan\": \"1.25.11\", \"versionType\": \"semver\"}, {\"status\": \"affected\", \"version\": \"1.26.0-0\", \"lessThan\": \"1.26.4\", \"versionType\": \"semver\"}], \"packageName\": \"mime\", \"collectionURL\": \"https://pkg.go.dev\", \"defaultStatus\": \"unaffected\", \"programRoutines\": [{\"name\": \"WordDecoder.DecodeHeader\"}]}], \"references\": [{\"url\": \"https://go.dev/issue/79217\"}, {\"url\": \"https://go.dev/cl/774481\"}, {\"url\": \"https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw\"}, {\"url\": \"https://pkg.go.dev/vuln/GO-2026-5038\"}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"description\": \"CWE-407: Inefficient Algorithmic Complexity\"}]}], \"providerMetadata\": {\"orgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"shortName\": \"Go\", \"dateUpdated\": \"2026-09-10T16:34:26.261Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-42504\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-09-10T16:34:26.261Z\", \"dateReserved\": \"2026-04-28T00:21:12.792Z\", \"assignerOrgId\": \"1bb62c36-49e3-4200-9d77-64a1400537cc\", \"datePublished\": \"2026-06-02T22:01:37.219Z\", \"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.