JwtClaims.MarshalJSON panics via reflect.StructOf when any untyped claim key is not a valid Go identifier suffix

{
  "id": "15cbc88c656628a0710d92833d7a566f23320b4ee7a99bb01992c1f56f4a9ce9",
  "url": "https://osv.dev/vulnerability/CVE-2026-89315",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "JwtClaims.MarshalJSON panics via reflect.StructOf when any untyped claim key is not a valid Go identifier suffix",
    "summary": "`JwtClaims.MarshalJSON` built a Go struct at runtime with `reflect.StructOf`, synthesising a field named `\"A\" + claimName` for each untyped claim. `reflect.StructOf` **panics** when a field name is not a valid Go identifier, or when it duplicates another field. Both conditions are reachable from ordinary JWT claim names.",
    "evidence": "osv:CVE-2026-89315",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-89315",
      "aliases": [
        "CVE-2026-89315",
        "GHSA-hwm6-rwv6-xgq8"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/eclipse-keypont/gose",
              "type": "GIT",
              "events": [
                {
                  "introduced": "5e7aba5b0fab2fedfac84d7ea04d8cabc92ec625"
                },
                {
                  "last_affected": "bc195a14438f6607e266d8a12e529260272b060b"
                },
                {
                  "introduced": "0"
                },
                {
                  "fixed": "692c25c38e72e91a146c00598017e1a869e75ef6"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0.7.3"
                      },
                      {
                        "last_affected": "0.13.0-rc1"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "1.0.0-rc4"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v0.12.1-rc1",
            "v0.12.0",
            "v0.13.0-rc1",
            "v0.10.0",
            "v0.9.1",
            "v0.9.0",
            "v0.8.7",
            "v0.8.6",
            "v0.8.5",
            "v0.8.4",
            "v0.8.3",
            "v0.8.2",
            "v0.8.1",
            "v0.8.0",
            "v0.7.8",
            "v0.7.7",
            "v0.7.6",
            "v0.7.5",
            "v0.7.4",
            "v0.7.3"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-89315.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:27.846472945Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89315.json",
        "https://github.com/eclipse-keypont/gose/security/advisories/GHSA-hwm6-rwv6-xgq8",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-89315"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-248"
        ],
        "cna_assigner": "eclipse",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/89xxx/CVE-2026-89315.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-89315",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 494489,
  "published_at": "2026-10-23T08:46:30.146+00:00"
}