{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:messagepack:messagepack:*:*:*:*:*:c\\#:*:*",
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "2.5.301"
              },
              {
                "introduced": "3.0.3"
              },
              {
                "fixed": "3.1.7"
              }
            ],
            "source": "CPE_RANGE"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5657b1e34ea2869a2ca6bc0aa6617158620201ba"
            },
            {
              "introduced": "ff3af77f546138d9da71707baddf2c30f55dfc15"
            },
            {
              "fixed": "1b53ae8b7681340199faf337bcbb0eb5aed702de"
            }
          ],
          "repo": "https://github.com/messagepack-csharp/messagepack-csharp",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-q2h6-ghwm-5qm8"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-407"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48516.json"
  },
  "details": "MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, InterfaceLookupFormatter\u003cTKey,TElement\u003e constructs an internal Dictionary\u003cTKey, IGrouping\u003cTKey,TElement\u003e\u003e with the default equality comparer instead of the security-aware comparer supplied by options.Security.GetEqualityComparer\u003cTKey\u003e(). This formatter omission allows hash-collision CPU denial of service against ILookup\u003cTKey,TElement\u003e even when the application has opted into the untrusted-data security posture This vulnerability is fixed in 2.5.301 and 3.1.7.",
  "id": "CVE-2026-48516",
  "modified": "2026-07-08T05:39:03.137761479Z",
  "published": "2026-06-22T21:09:51.787Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48516.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/MessagePack-CSharp/MessagePack-CSharp/security/advisories/GHSA-q2h6-ghwm-5qm8"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-48516"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "MessagePack-CSharp: InterfaceLookupFormatter bypasses collision-resistant comparer settings"
}