concurrent-ruby: `AtomicReference#update` livelocks when the stored value is `Float::NAN`_CVE-2026-54904

{
    "lastseen": "",
    "description": "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.",
    "published": "2026-06-24T15:44:21.992Z",
    "modified": "2026-06-24T15:44:21.992Z",
    "type": "cve",
    "title": "concurrent-ruby:  `AtomicReference#update` livelocks when the stored value is `Float::NAN`",
    "source": "GitHub_M",
    "references": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-h8w8-99g7-qmvj",
    "id": "CVE-2026-54904",
    "bulletinFamily": "",
    "cwe": [
        "CWE-835"
    ],
    "cvelist": null,
    "sourceData": "ruby-concurrency concurrent-ruby < 1.3.7",
    "sourceHref": "",
    "cvss": {
        "score": 8.2,
        "severity": "HIGH",
        "vector": "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",
        "version": "4.0"
    },
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    "href": "",
    "category_name": "CVE",
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    "product": "concurrent-ruby",
    "version": "< 1.3.7",
    "vendor": "ruby-concurrency",
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}