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CVE-2026-55107

Status: DeferredCritical (10)—

Kobako is a Ruby gem that embeds a Wasm-isolated mruby interpreter inside applications, allowing execution of untrusted Ruby scripts (LLM-generated code, user formulas, student submissions, third-party plugins) in-process without giving them access to host memory, files, network, or credentials. From version 0.1.0 to before version 0.9.1, a guest mruby script running inside the Kobako sandbox can execute arbitrary Ruby in the host process, fully escaping the sandbox. This issue has been patched in version 0.9.1.

CVSS

Exploitation probability (EPSS)

FIRST hasn't scored this CVE yet (usual for very recent or rejected CVEs).

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).

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Kobako — KobakoAI

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2026-55107",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55107",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-30T19:48:55.982496Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "CHANGED",
          "version": "3.1",
          "baseScore": 10,
          "attackVector": "NETWORK",
          "baseSeverity": "CRITICAL",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "elct9620",
          "product": "kobako",
          "versions": [
            {
              "status": "affected",
              "version": ">= 0.1.0, < 0.9.1"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-09-30T18:18:37.550",
  "references": [
    {
      "url": "https://github.com/elct9620/kobako/commit/64f84700c81f44902bed9211318d5362f44987b3",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/elct9620/kobako/releases/tag/v0.9.1",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h",
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/elct9620/kobako/security/advisories/GHSA-7pwq-q9jf-539h",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ],
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-94"
        },
        {
          "lang": "en",
          "value": "CWE-470"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Kobako is a Ruby gem that embeds a Wasm-isolated mruby interpreter inside applications, allowing execution of untrusted Ruby scripts (LLM-generated code, user formulas, student submissions, third-party plugins) in-process without giving them access to host memory, files, network, or credentials. From version 0.1.0 to before version 0.9.1, a guest mruby script running inside the Kobako sandbox can execute arbitrary Ruby in the host process, fully escaping the sandbox. This issue has been patched in version 0.9.1."
    }
  ],
  "lastModified": "2026-09-30T20:17:32.923",
  "sourceIdentifier": "security-advisories@github.com"
}