ruby-concurrent — security advisory
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.
- Products
- ruby-concurrent
- Affected versions
- 1.1.6+dfsg-5, 1.2.3-1, 1.2.3-2, 1.2.3-3, 1.2.3-4, 1.3.4-1, 1.3.4-1~exp1, 1.3.5-1, 1.3.6-1, 1.3.7-1, 1.3.7-2, 1.3.7-3, 1.3.7-4, 1.3.8-1
- Fixed versions
- 1.3.7-1
- CVEs
- CVE-2026-54904
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 12:20 UTC · Revision 2
Source evidence
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.
osv:DEBIAN-CVE-2026-54904
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: 1.3.7-1
Complete source record
{
"id": "5256c04ea0a59474208ec7b374a8188ef863c920765d4cf8cf75ad2c14897402",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-54904",
"method": "structured",
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"title": "DEBIAN-CVE-2026-54904",
"summary": "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.",
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"modified": "2026-10-26T11:47:39.218656561Z",
"provider": "osv",
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"source_id": "core-osv",
"document_id": 450878,
"published_at": "2026-06-24T17:17:29.267+00:00"
}