{
  "crds_version": "0.1",
  "kind": "base",
  "id": "crds:cve-2023-33009",
  "revision": 1,
  "title": "Zyxel firewalls — overflow in the notification function",
  "summary": "A buffer overflow in the notification function of Zyxel's firewall firmware lets an attacker with no credentials crash the device or execute code on it. Firmware from 4.60 up to 5.36 Patch 1 is affected across the product line.",
  "source_type": "cve",
  "severity": "critical",
  "cvss": {
    "score": 9.8,
    "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
    "version": "3.1"
  },
  "epss": 0.28144,
  "exploitation": {
    "known_exploited": true,
    "exploit_available": false,
    "attack_complexity": "low",
    "kev_added": "2023-06-05",
    "prerequisites": "Network access to the affected service on the device."
  },
  "remediation": {
    "patch_available": true
  },
  "mitre_attack": [
    "T1190"
  ],
  "kill_chain": "initial_access",
  "recommended_action": "Update the firewall firmware past 5.36 Patch 1, and keep the management and remote access services off the public internet while the rollout runs.",
  "confidence": "high",
  "provenance": [
    {
      "fields": [
        "cvss",
        "exploitation.attack_complexity",
        "exploitation.exploit_available",
        "references",
        "published_at"
      ],
      "source": "https://nvd.nist.gov/vuln/detail/CVE-2023-33009",
      "retrieved_at": "2026-09-24T12:52:19.575Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
        "exploitation.known_exploited",
        "exploitation.kev_added"
      ],
      "source": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "retrieved_at": "2026-09-24T12:52:19.575Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
        "epss"
      ],
      "source": "https://api.first.org/data/v1/epss?cve=CVE-2023-33009",
      "retrieved_at": "2026-09-24T12:52:19.575Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
        "title",
        "summary",
        "severity",
        "remediation",
        "mitre_attack",
        "kill_chain",
        "recommended_action",
        "confidence",
        "tags",
        "exploitation.prerequisites"
      ],
      "source": "https://nvd.nist.gov/vuln/detail/CVE-2023-33009",
      "retrieved_at": "2026-09-24T12:52:19.575Z",
      "confidence": "high",
      "extractor": "claude-code"
    }
  ],
  "references": [
    {
      "type": "cve",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-33009",
      "label": "NVD record"
    },
    {
      "type": "cisa",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "label": "CISA Known Exploited Vulnerabilities catalog"
    },
    {
      "type": "vendor_advisory",
      "url": "https://www.zyxel.com/global/en/support/security-advisories/zyxel-security-advisory-for-multiple-buffer-overflow-vulnerabilities-of-firewalls"
    }
  ],
  "published_at": "2023-05-24T13:15:09.560Z",
  "issued_at": "2026-09-24T12:52:19.575Z",
  "tags": [
    "zyxel",
    "firewall",
    "buffer-overflow",
    "network-device",
    "kev"
  ]
}