Ruby JSON: JSON generator heap buffer overflow when streaming to an IO

{
  "id": "f9b7f92cd7cdb6ddbbbb7b879d76c6ab63dde5f1ff2f967cfac009a3bea39cd2",
  "url": "https://osv.dev/vulnerability/CVE-2026-54696",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Ruby JSON: JSON generator heap buffer overflow when streaming to an IO",
    "summary": "Ruby JSON is a JSON implementation for Ruby. Versions 2.9.0 through 2.19.8 are vulnerable to heap buffer overflow when the JSON generator is provided with an oversized streamed object. When streaming to an IO JSON.dump(obj, io) and JSON::State#generate(obj, io) can write past the internal JSON generator buffer when a streamed object contains an attacker-controlled string near 16 KB. Exploitation would result in a reliable process crash/denial of service. This issue has been fixed in version 2.19.9.",
    "evidence": "osv:CVE-2026-54696",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-54696",
      "aliases": [
        "CVE-2026-54696",
        "GHSA-x2f5-4prf-w687"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/ruby/json",
              "type": "GIT",
              "events": [
                {
                  "introduced": "20b501a31d824449148c97385eb064f6f62ba127"
                },
                {
                  "last_affected": "5233dd9b851a4924f793aec1a1658ed8b66a34c7"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "2.9.0"
                      },
                      {
                        "last_affected": "2.19.8"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.19.8",
            "v2.19.7",
            "v2.19.6",
            "v2.19.5",
            "v2.19.4",
            "v2.19.2",
            "v2.15.2",
            "v2.17.1",
            "v2.19.1",
            "v2.19.0",
            "v2.18.1",
            "v2.18.0",
            "v2.17.0",
            "v2.16.0",
            "v2.15.1",
            "v2.15.0",
            "v2.14.1",
            "v2.14.0",
            "v2.13.2",
            "v2.13.1",
            "v2.13.0",
            "v2.12.2",
            "v2.12.1",
            "v2.12.0",
            "v2.11.3",
            "v2.11.2",
            "v2.11.1",
            "v2.11.0",
            "v2.10.2",
            "v2.10.1",
            "v2.10.0",
            "v2.9.1",
            "v2.9.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54696.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:37.411959123Z",
      "provider": "osv",
      "references": [
        "https://github.com/ruby/json/releases/tag/v2.19.9",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54696.json",
        "https://github.com/ruby/json/security/advisories/GHSA-x2f5-4prf-w687",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-54696"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-122",
          "CWE-131",
          "CWE-787"
        ],
        "cna_assigner": "GitHub_M",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "2.9.0"
                  },
                  {
                    "fixed": "2.19.9"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StringRangeExpression"
              }
            ]
          },
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "fixed": "2.19.9"
                  }
                ],
                "source": "DESCRIPTION"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54696.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-54696",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 504880,
  "published_at": "2026-06-30T22:05:48.347+00:00"
}