{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "cpe": "cpe:2.3:a:rubyconcurrency:concurrent_ruby:*:*:*:*:*:ruby:*:*",
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "1.3.7"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "CPE_RANGE"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4c8fc28ab6bb9bd8258a4c0c2fa6d35ebe77b3cb"
            }
          ],
          "repo": "https://github.com/ruby-concurrency/concurrent-ruby",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-h8w8-99g7-qmvj"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-835"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54904.json"
  },
  "details": "concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::AtomicReference#update can enter a permanent busy retry loop when the current value is Float::NAN. The issue is caused by the interaction between AtomicReference#update, which retries until compare_and_set(old_value, new_value) succeeds; Numeric compare_and_set, which checks old == old_value before attempting the underlying atomic swap.; and Ruby NaN semantics, where Float::NAN == Float::NAN is always false. As a result, once an AtomicReference contains Float::NAN, calling #update repeatedly evaluates the caller's block and never returns. In services that store externally derived numeric values in an AtomicReference, this can cause CPU exhaustion or permanent request/job hangs. This vulnerability is fixed in 1.3.7.",
  "id": "CVE-2026-54904",
  "modified": "2026-07-08T05:38:54.175550282Z",
  "published": "2026-06-24T15:44:21.992Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54904.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-h8w8-99g7-qmvj"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54904"
    }
  ],
  "schema_version": "1.7.5",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "concurrent-ruby:  `AtomicReference#update` livelocks when the stored value is `Float::NAN`"
}