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CVE-2026-83742

Estado: RecibidaMedia (5.3)—

Unsigned integer underflow in wstrncat() in src/port.c in wolfSSL wolfSSH from v1.4.11 through v1.5.0 on non-Windows platforms allows an authenticated remote attacker to write one out-of-bounds null byte past the end of a stack buffer by sending a crafted SFTP path. wolfSSH_RealPath() in src/ssh.c appends each path component with a remaining-size bound (outSz - curSz) rather than the full destination size, so once the accumulated path reaches half the output buffer the size_t computation n - strlen(s1) - 1 wraps to near SIZE_MAX.

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The strncat() call is then effectively unbounded and copies the whole component; when that component exactly fills the remainder of the buffer, its terminating null is written one byte past the end. The caller's own length check keeps the copied data inside the buffer, so the overflow is limited to that single null byte, which may corrupt an adjacent stack value and crash the process. Applications that call the public wolfSSH_RealPath() with an output buffer smaller than the input path are additionally exposed to an unbounded copy, because the word32 expression outSz - segSz in that length check also wraps.

CVSS

Probabilidad de explotación (EPSS)

FIRST aún no ha puntuado esta CVE (habitual en CVEs muy recientes o rechazadas).

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.

Atacante autenticado remoto explota underflow en wstrncat() vía SFTP path (AV:N, PR:L, red); corrupción de buffer stack puede escalar privilegios o causar DoS.

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

Threat Intelligence ProgramApplication Isolation and SandboxingExploit ProtectionUpdate SoftwareVulnerability ScanningPrivileged Account Management

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Wolfssl — WolfsshAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-83742",
  "cveTags": [],
  "metrics": {
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "facts@wolfssl.com",
        "cvssData": {
          "Safety": "NOT_DEFINED",
          "version": "4.0",
          "Recovery": "NOT_DEFINED",
          "baseScore": 5.3,
          "Automatable": "NO",
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:X/V:X/RE:X/U:X",
          "exploitMaturity": "NOT_DEFINED",
          "providerUrgency": "NOT_DEFINED",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "privilegesRequired": "LOW",
          "subIntegrityImpact": "NONE",
          "vulnIntegrityImpact": "LOW",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "vulnAvailabilityImpact": "LOW",
          "availabilityRequirement": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "subConfidentialityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "facts@wolfssl.com",
      "affectedData": [
        {
          "repo": "https://github.com/wolfSSL/wolfssh",
          "vendor": "wolfSSL Inc.",
          "product": "wolfSSH",
          "versions": [
            {
              "status": "affected",
              "changes": [
                {
                  "at": "1.6.0",
                  "status": "unaffected"
                }
              ],
              "version": "1.4.11",
              "versionType": "semver",
              "lessThanOrEqual": "1.5.0"
            }
          ],
          "programFiles": [
            "src/port.c",
            "src/ssh.c"
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-10-07T03:16:59.880",
  "references": [
    {
      "url": "https://github.com/wolfSSL/wolfssh/commit/513e52b18927a4e3f7cf17ecaf107958e56139de",
      "source": "facts@wolfssl.com"
    },
    {
      "url": "https://github.com/wolfSSL/wolfssh/commit/822e4464560b467580ea37a2fc03b0988d88b71f",
      "source": "facts@wolfssl.com"
    },
    {
      "url": "https://github.com/wolfSSL/wolfssh/commit/fbc7cd88a23b59a45a584020a4c7242d9bd70f35",
      "source": "facts@wolfssl.com"
    },
    {
      "url": "https://github.com/wolfSSL/wolfssh/pull/1084",
      "source": "facts@wolfssl.com"
    }
  ],
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "facts@wolfssl.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-121"
        },
        {
          "lang": "en",
          "value": "CWE-191"
        },
        {
          "lang": "en",
          "value": "CWE-193"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Unsigned integer underflow in wstrncat() in src/port.c in wolfSSL wolfSSH from v1.4.11 through v1.5.0 on non-Windows platforms allows an authenticated remote attacker to write one out-of-bounds null byte past the end of a stack buffer by sending a crafted SFTP path. wolfSSH_RealPath() in src/ssh.c appends each path component with a remaining-size bound (outSz - curSz) rather than the full destination size, so once the accumulated path reaches half the output buffer the size_t computation n - strlen(s1) - 1 wraps to near SIZE_MAX. The strncat() call is then effectively unbounded and copies the whole component; when that component exactly fills the remainder of the buffer, its terminating null is written one byte past the end. The caller's own length check keeps the copied data inside the buffer, so the overflow is limited to that single null byte, which may corrupt an adjacent stack value and crash the process. Applications that call the public wolfSSH_RealPath() with an output buffer smaller than the input path are additionally exposed to an unbounded copy, because the word32 expression outSz - segSz in that length check also wraps."
    }
  ],
  "lastModified": "2026-10-07T03:16:59.880",
  "sourceIdentifier": "facts@wolfssl.com"
}