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Vulnerability Details CVE-2026-54904

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.

Exploit prediction scoring system (EPSS) score

EPSS Score 0.003

EPSS Ranking 19.5%

CVSS Severity

CVSS v3 Score 7.5

References

Products affected by CVE-2026-54904

Rubyconcurrency » Concurrent Ruby » Version: 0.0.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.0.1
Rubyconcurrency » Concurrent Ruby » Version: 0.0.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.0.2
Rubyconcurrency » Concurrent Ruby » Version: 0.1.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.1.0
Rubyconcurrency » Concurrent Ruby » Version: 0.1.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.1.1
Rubyconcurrency » Concurrent Ruby » Version: 0.2.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.2.0
Rubyconcurrency » Concurrent Ruby » Version: 0.2.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.2.1
Rubyconcurrency » Concurrent Ruby » Version: 0.2.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.2.2
Rubyconcurrency » Concurrent Ruby » Version: 0.3.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.3.0
Rubyconcurrency » Concurrent Ruby » Version: 0.3.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.3.1
Rubyconcurrency » Concurrent Ruby » Version: 0.3.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.3.2
Rubyconcurrency » Concurrent Ruby » Version: 0.4.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.4.0
Rubyconcurrency » Concurrent Ruby » Version: 0.4.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.4.1
Rubyconcurrency » Concurrent Ruby » Version: 0.5.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.5.0
Rubyconcurrency » Concurrent Ruby » Version: 0.6.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.6.0
Rubyconcurrency » Concurrent Ruby » Version: 0.6.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.6.1
Rubyconcurrency » Concurrent Ruby » Version: 0.7.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.7.0
Rubyconcurrency » Concurrent Ruby » Version: 0.7.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.7.2
Rubyconcurrency » Concurrent Ruby » Version: 0.8.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.8.0
Rubyconcurrency » Concurrent Ruby » Version: 0.9.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.9.0
Rubyconcurrency » Concurrent Ruby » Version: 0.9.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.9.1
Rubyconcurrency » Concurrent Ruby » Version: 0.9.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:0.9.2
Rubyconcurrency » Concurrent Ruby » Version: 1.0.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.0.0
Rubyconcurrency » Concurrent Ruby » Version: 1.0.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.0.1
Rubyconcurrency » Concurrent Ruby » Version: 1.0.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.0.2
Rubyconcurrency » Concurrent Ruby » Version: 1.0.3

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.0.3
Rubyconcurrency » Concurrent Ruby » Version: 1.0.4

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.0.4
Rubyconcurrency » Concurrent Ruby » Version: 1.0.5

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.0.5
Rubyconcurrency » Concurrent Ruby » Version: 1.1.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.0
Rubyconcurrency » Concurrent Ruby » Version: 1.1.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.1
Rubyconcurrency » Concurrent Ruby » Version: 1.1.10

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.10
Rubyconcurrency » Concurrent Ruby » Version: 1.1.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.2
Rubyconcurrency » Concurrent Ruby » Version: 1.1.3

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.3
Rubyconcurrency » Concurrent Ruby » Version: 1.1.4

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.4
Rubyconcurrency » Concurrent Ruby » Version: 1.1.5

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.5
Rubyconcurrency » Concurrent Ruby » Version: 1.1.6

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.6
Rubyconcurrency » Concurrent Ruby » Version: 1.1.7

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.7
Rubyconcurrency » Concurrent Ruby » Version: 1.1.8

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.8
Rubyconcurrency » Concurrent Ruby » Version: 1.1.9

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.1.9
Rubyconcurrency » Concurrent Ruby » Version: 1.2.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.2.0
Rubyconcurrency » Concurrent Ruby » Version: 1.2.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.2.1
Rubyconcurrency » Concurrent Ruby » Version: 1.2.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.2.2
Rubyconcurrency » Concurrent Ruby » Version: 1.2.3

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.2.3
Rubyconcurrency » Concurrent Ruby » Version: 1.3.0

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.0
Rubyconcurrency » Concurrent Ruby » Version: 1.3.1

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.1
Rubyconcurrency » Concurrent Ruby » Version: 1.3.2

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.2
Rubyconcurrency » Concurrent Ruby » Version: 1.3.3

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.3
Rubyconcurrency » Concurrent Ruby » Version: 1.3.4

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.4
Rubyconcurrency » Concurrent Ruby » Version: 1.3.5

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.5
Rubyconcurrency » Concurrent Ruby » Version: 1.3.6

cpe:2.3:a:rubyconcurrency:concurrent_ruby:1.3.6

Vulnerabilities

Vulnerable Software

Vulnerability Details CVE-2026-54904

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