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CVE-2018-18556

Status: ModifiedCritical (9.9)—Exploit
Severity9.9Critical · CVSS 3.1
Exploitation probability15 %higher than 97% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitAvailableMetasploit module (reliable, widely available exploit)

A privilege escalation issue was discovered in VyOS 1.1.8. The default configuration also allows operator users to execute the pppd binary with elevated (sudo) permissions. Certain input parameters are not properly validated. A malicious operator user can run the binary with elevated permissions and leverage its improper input validation condition to spawn an attacker-controlled shell with root privileges.

CVSS

Base score
9.9
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
15 %
Percentile among all scored CVEs
97
Score date
10/27/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Public exploits

Exploit code or detection templates are publicly available. This is not the same as confirmed active exploitation (KEV), but it raises the risk: patch with priority.

Affected technologies (1)

Vyos — Vyos

CWEs

References

Show 6 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2018-18556",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 9,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:S/C:C/I:C/A:C",
          "authentication": "SINGLE",
          "integrityImpact": "COMPLETE",
          "accessComplexity": "LOW",
          "availabilityImpact": "COMPLETE",
          "confidentialityImpact": "COMPLETE"
        },
        "acInsufInfo": false,
        "impactScore": 10,
        "baseSeverity": "HIGH",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 9.9,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 6,
        "exploitabilityScore": 3.1
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2018-12-17T19:29:00.627",
  "references": [
    {
      "url": "http://packetstormsecurity.com/files/159234/VyOS-restricted-shell-Escape-Privilege-Escalation.html",
      "tags": [
        "Exploit",
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://blog.mirch.io/2018/11/05/cve-2018-18556-vyos-privilege-escalation-via-sudo-pppd-for-operator-users/",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://blog.vyos.io/the-operator-level-is-proved-insecure-and-will-be-removed-in-the-next-releases",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "http://packetstormsecurity.com/files/159234/VyOS-restricted-shell-Escape-Privilege-Escalation.html",
      "tags": [
        "Exploit",
        "Third Party Advisory",
        "VDB Entry"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://blog.mirch.io/2018/11/05/cve-2018-18556-vyos-privilege-escalation-via-sudo-pppd-for-operator-users/",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://blog.vyos.io/the-operator-level-is-proved-insecure-and-will-be-removed-in-the-next-releases",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "NVD-CWE-noinfo"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A privilege escalation issue was discovered in VyOS 1.1.8. The default configuration also allows operator users to execute the pppd binary with elevated (sudo) permissions. Certain input parameters are not properly validated. A malicious operator user can run the binary with elevated permissions and leverage its improper input validation condition to spawn an attacker-controlled shell with root privileges."
    },
    {
      "lang": "es",
      "value": "Se ha descubierto un problema de escalado de privilegios en VyOS 1.1.8. La configuración por defecto también permite que los usuarios operadores ejecuten el binario pppd con permisos elevados (sudo). Ciertos parámetros de entrada no se validan correctamente. Un usuario operador malicioso puede ejecutar el binario con permisos elevados y aprovechar su condición de validación incorrecta para lanzar un shell controlado por el atacante con privilegios root."
    }
  ],
  "lastModified": "2026-06-17T01:47:29.840",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:vyos:vyos:1.1.8:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "7959038B-A2A9-49EE-9684-56209F2A7CC2"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}