{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.7.0"
              }
            ],
            "source": [
              "DESCRIPTION",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4007498b13582d90ee1eda5d9920c324428b98b3"
            },
            {
              "fixed": "f47ad47c7b5745b53d3f9ac711a5a419a272a5d7"
            }
          ],
          "repo": "https://github.com/bcgit/bc-csharp",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "bcorg",
    "cwe_ids": [
      "CWE-789"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/103xxx/CVE-2026-103603.json"
  },
  "details": "Memory allocation with excessive size value in the HSS/LMS signature code (HssPublicKeyParameters, HssSignature) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows a remote unauthenticated attacker who can supply both an HSS public key and a signature to cause a denial of service through memory exhaustion via a public key encoding with an excessive level count, because the level count L read when parsing an HSS public key was not checked against the RFC 8554 maximum of 8, and signature parsing then allocated an array of L - 1 entries before reading any further signature data. A single verification can commit up to about 17 GB of memory or fail with an OutOfMemoryException.",
  "id": "CVE-2026-103603",
  "modified": "2026-10-04T02:30:48.739762832Z",
  "published": "2026-10-02T07:10:34.017Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://www.nuget.org/packages/BouncyCastle.Cryptography"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/103xxx/CVE-2026-103603.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/bcgit/bc-csharp/wiki/CVE-2026-103603"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-103603"
    },
    {
      "type": "FIX",
      "url": "https://github.com/bcgit/bc-csharp/commit/f47ad47c7b5745b53d3f9ac711a5a419a272a5d7"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/bcgit/bc-csharp"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Unbounded HSS public key level count allows huge array allocation during signature verification"
}