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CVE-2026-39834

Estado: AnalizadaCrítica (9.1)—

When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

AV:N/PR:N/UI:N con desbordamiento de enteros causa bucle infinito (DoS) en SSH remoto. Escalada si aprovecha para ejecución privilegiada.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Filter Network TrafficVulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkApplication Isolation and Sandboxing

Tecnologías afectadas (1)

Golang — Crypto

CWE

Referencias

JSON original (NVD)

Mostrar
{
  "id": "CVE-2026-39834",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-39834",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-05-22T18:50:30.848292Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 9.1,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security@golang.org",
      "affectedData": [
        {
          "vendor": "golang.org/x/crypto",
          "product": "golang.org/x/crypto/ssh",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "lessThan": "0.52.0",
              "versionType": "semver"
            }
          ],
          "packageName": "golang.org/x/crypto/ssh",
          "collectionURL": "https://pkg.go.dev",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "channel.WriteExtended"
            },
            {
              "name": "Dial"
            },
            {
              "name": "NewClientConn"
            },
            {
              "name": "NewServerConn"
            },
            {
              "name": "Session.CombinedOutput"
            },
            {
              "name": "Session.Output"
            },
            {
              "name": "Session.Run"
            },
            {
              "name": "Session.Shell"
            },
            {
              "name": "Session.Start"
            },
            {
              "name": "channel.Write"
            },
            {
              "name": "curve25519sha256.Client"
            },
            {
              "name": "curve25519sha256.Server"
            },
            {
              "name": "dhGEXSHA.Client"
            },
            {
              "name": "dhGEXSHA.Server"
            },
            {
              "name": "dhGroup.Client"
            },
            {
              "name": "dhGroup.Server"
            },
            {
              "name": "ecdh.Client"
            },
            {
              "name": "ecdh.Server"
            },
            {
              "name": "extChannel.Write"
            },
            {
              "name": "mlkem768WithCurve25519sha256.Client"
            },
            {
              "name": "mlkem768WithCurve25519sha256.Server"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-05-22T04:16:24.237",
  "references": [
    {
      "url": "https://go.dev/cl/781663",
      "tags": [
        "Issue Tracking"
      ],
      "source": "security@golang.org"
    },
    {
      "url": "https://go.dev/issue/79567",
      "tags": [
        "Issue Tracking"
      ],
      "source": "security@golang.org"
    },
    {
      "url": "https://groups.google.com/g/golang-announce/c/a082jnz-LvI",
      "tags": [
        "Mailing List"
      ],
      "source": "security@golang.org"
    },
    {
      "url": "https://pkg.go.dev/vuln/GO-2026-5020",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "security@golang.org"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-190"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "When writing data larger than 4GB in a single Write call on an SSH channel, an integer overflow in the internal payload size calculation caused the write loop to spin indefinitely, sending empty packets without making progress. The size comparison now uses int64 to prevent truncation."
    },
    {
      "lang": "es",
      "value": "Al escribir datos mayores de 4 GB en una sola llamada Write en un canal SSH, un desbordamiento de entero en el cálculo interno del tamaño de la carga útil hizo que el bucle de escritura girara indefinidamente, enviando paquetes vacíos sin avanzar. La comparación de tamaño ahora usa int64 para evitar la truncación."
    }
  ],
  "lastModified": "2026-07-23T16:10:00.137",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:golang:crypto:*:*:*:*:*:go:*:*",
              "vulnerable": true,
              "matchCriteriaId": "D540395B-31B8-4B07-8F79-F5C631BBD5C8",
              "versionEndExcluding": "0.52.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security@golang.org"
}