Skip to main content
VulnerabilityPublished Updated

CVE-2026-54904: concurrent-ruby · Infinite Loop

Affects concurrent-rubySource CVE Database V5

0
Compare

Not known to be exploited · CVSS 8.2 High : upgrade to 1.3.7 soon.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 52% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.3.7
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade concurrent-ruby to 1.3.7.

Affected software

ProductAffectedFixed in
ruby-concurrencyconcurrent-rubyAffected
  • <1.3.7
Fixed in
  • 1.3.7
RubyGemsconcurrent-rubypkg:gem/concurrent-rubyOther threatsAffected
  • <1.3.7
Fixed in
  • 1.3.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade concurrent-ruby to version 1.3.7 or later, where this infinite loop issue is fixed. No other mitigations are indicated by the vendor advisory. Patch status is confirmed fixed in 1.3.7.

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.

References

Community reviews

Loading reviews…