{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2026-42770",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2026-42770",
    "idYear": 2026,
    "status": "PUBLISHED",
    "publishedAt": "2026-06-09T16:03:29.802Z",
    "updatedAt": "2026-07-20T16:09:50.313Z",
    "importedAt": "2026-10-24T01:58:08.712Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "FFC-DH Peer Validation Uses Attacker-Supplied q",
      "summary": "Issue summary: When EVP_PKEY_derive_set_peer() is called with a DHX (X9.42)\npeer key, the peer key is not properly checked for the subgroup membership.\n\nImpact summary: A malicious peer which presents an X9.42 key carrying the\nvictim's p and g parameters, a forged q = r (a small prime factor of the\ncofactor (p−1)/q_local), and a public value Y of order r can recover the\nvictim's private key after a small number of key exchange attempts.\n\nWhen EVP_PKEY_derive_set_peer() is called with a DHX (X9.42) peer key, the\nsubgroup membership check Y^q ≡ 1 (mod p) is performed using the peer's\nown q parameter, not the local key's q. The peer's domain parameters are\nthen matched against the domain parameters of the private key, but the value\nof q is not compared.\n\nA malicious peer who presents an X9.42 key carrying the victim's p, g,\na forged q = r (a small prime factor of the cofactor), and a public\nvalue Y of order r passes all checks. The shared secret then takes only\nr distinct values, leaking priv mod r. Repeating for each small-prime\nfactor of the cofactor and combining via CRT recovers the full private\nkey (Lim–Lee / small-subgroup-confinement attack).\n\nThe realistic attack surface is narrow: principally CMP deployments with\nlong-lived RA/CA DHX keys and bespoke enterprise or government applications\nusing X9.42 DHX static keys with interactive protocols and therefore this\nissue was assigned Low severity.\n\nThe FIPS modules in 4.0, 3.6, 3.5, 3.4, 3.1.2 and 3.0 are affected by this\nissue.",
      "affected": [
        {
          "vendor": "OpenSSL",
          "product": "OpenSSL",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "4.0.0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.0.1"
            },
            {
              "version": "3.6.0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "3.6.3"
            },
            {
              "version": "3.5.0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "3.5.7"
            },
            {
              "version": "3.4.0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "3.4.6"
            },
            {
              "version": "3.0.0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "3.0.21"
            }
          ]
        }
      ]
    }
  }
}