CVE-2026-103603

{
  "etk_id": "ETK-2026-330",
  "cve_id": "CVE-2026-103603",
  "display_id": "CVE-2026-103603",
  "ghsa_id": "GHSA-gpr4-c479-xrw4",
  "euvd_id": "EUVD-2026-91233",
  "status": "published",
  "anchor_state": "anchored",
  "title": "Excessive memory allocation in bc-csharp HSS/LMS parsing",
  "summary": "bc-csharp versions earlier than 2.7.0 can allocate excessive memory while processing HSS/LMS public keys and signatures. An unauthenticated attacker may cause a denial of service if they can provide both a public key and signature to a verification operation.",
  "mitigation": "Upgrade bc-csharp to version 2.7.0 or later. Until upgraded, restrict verification endpoints to trusted sources and reject untrusted HSS/LMS key and signature inputs.",
  "vendor": "legion of the bouncy castle inc.",
  "product": "bc-csharp",
  "affected": [
    {
      "affected_notes": [],
      "affected_ranges": [
        ">= 0, < 2.7.0"
      ],
      "ecosystem": null,
      "fixed_versions": [
        "2.7.0"
      ],
      "package_name": "BouncyCastle.Cryptography",
      "purl": null
    }
  ],
  "cwes": null,
  "cvss_score": 8.7,
  "cvss_src": "cna_vendor",
  "cvss_vector": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
  "epss_score": 0.0041,
  "epss_percentile": 0.3408,
  "epss_asof": "2026-10-20",
  "automation": "contextual",
  "check": true,
  "check_confidence_basis": "mechanism_verified",
  "exploit": false,
  "pipeline_minutes": 12.1402052,
  "t0_at": "2026-10-02T07:10:34.017000+00:00",
  "signals": {
    "check": {
      "at": "2026-10-02T11:35:44.162822+00:00",
      "days": 0.18414520627314815,
      "is_lower_bound": false,
      "measured_at": "2026-10-02T07:10:34.017000+00:00",
      "url": null
    },
    "trigger_signal": {
      "at": "2026-10-02T07:10:34.017000+00:00",
      "days": 0,
      "is_lower_bound": false,
      "measured_at": "2026-10-02T07:10:34.017000+00:00",
      "url": "https://github.com/advisories/GHSA-gpr4-c479-xrw4"
    }
  }
}