{
  "crds_version": "0.1",
  "kind": "base",
  "id": "crds:cve-2015-4000",
  "revision": 1,
  "title": "Logjam — Downgrade to Export-Grade Key Exchange",
  "summary": "A server that still offers export-grade key exchange can be talked down to it by a network attacker, who then breaks the weakened key and reads or alters the connection.",
  "source_type": "cve",
  "severity": "low",
  "cvss": {
    "score": 3.7,
    "vector": "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N",
    "version": "3.0"
  },
  "epss": 0.9986,
  "exploitation": {
    "known_exploited": false,
    "exploit_available": false,
    "attack_complexity": "high",
    "prerequisites": "A position on the network path"
  },
  "remediation": {
    "patch_available": true
  },
  "mitre_attack": [
    "T1557"
  ],
  "kill_chain": "credential_access",
  "recommended_action": "Remove export-grade key exchange from every server, and require groups of at least 2048 bits.",
  "confidence": "high",
  "provenance": [
    {
      "fields": [
        "cvss",
        "exploitation.attack_complexity",
        "exploitation.exploit_available",
        "references",
        "published_at"
      ],
      "source": "https://nvd.nist.gov/vuln/detail/CVE-2015-4000",
      "retrieved_at": "2026-08-07T16:57:17.024Z",
      "confidence": "high",
      "extractor": "scrty-crds-pipeline/0.1"
    },
    {
      "fields": [
        "epss"
      ],
      "source": "https://api.first.org/data/v1/epss?cve=CVE-2015-4000",
      "retrieved_at": "2026-08-07T16:57:17.024Z",
      "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-2015-4000",
      "retrieved_at": "2026-08-07T16:57:17.024Z",
      "confidence": "high",
      "extractor": "claude-code"
    }
  ],
  "references": [
    {
      "type": "cve",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2015-4000",
      "label": "NVD record"
    },
    {
      "type": "vendor_advisory",
      "url": "http://www.oracle.com/technetwork/security-advisory/cpuapr2016v3-2985753.html"
    },
    {
      "type": "vendor_advisory",
      "url": "http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html"
    },
    {
      "type": "vendor_advisory",
      "url": "https://openssl.org/news/secadv/20150611.txt"
    },
    {
      "type": "vendor_advisory",
      "url": "https://www.openssl.org/blog/blog/2015/05/20/logjam-freak-upcoming-changes/"
    }
  ],
  "published_at": "2015-05-21T00:59:00.087Z",
  "issued_at": "2026-08-07T16:57:17.024Z",
  "tags": [
    "cryptography",
    "protocol",
    "downgrade"
  ]
}