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CVE-2026-54904

Rubyconcurrency Concurrent Ruby denial of service

7.5 HIGHPublic exploitEPSS 0.67%
  1. Published24 Jun 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

Rubyconcurrency Concurrent Ruby< 1.3.7

Remediation

Fixed in
Rubyconcurrency Concurrent Ruby≥ 1.3.7

References

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Frequently asked

Is CVE-2026-54904 being actively exploited?

CVE-2026-54904 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.67%.

How severe is CVE-2026-54904?

CVE-2026-54904 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.67% probability of exploitation.

Which products are affected by CVE-2026-54904?

Affected products include Rubyconcurrency Concurrent Ruby.

How do I fix CVE-2026-54904?

Upgrade affected software to a fixed version, for example Rubyconcurrency Concurrent Ruby 1.3.7 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-54904 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.