CVE-2026-54904Public exploitNetwork attack vector

CPU exhaustion via NaN comparison retry loop

Published Jun 24, 2026 · Updated Jun 24, 2026

Denial of service in ruby-concurrency concurrent-ruby before 1.3.7 allows remote attackers to hang applications via a NaN value. Concurrent::AtomicReference#update retries until compare_and_set succeeds, but the numeric wrapper rejects NaN because Ruby equality reports NaN unequal to itself. Exposure requires an application to store externally derived numeric data in the reference; a later update spins indefinitely, consuming CPU and hanging the request or job.

CVSS severity8.2
High
EPSS probability0.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in ruby-concurrency concurrent-ruby before 1.3.7 allows remote attackers to hang applications via a NaN value. Concurrent::AtomicReference#update retries until compare_and_set succeeds, but the numeric wrapper rejects NaN because Ruby equality reports NaN unequal to itself. Exposure requires an application to store externally derived numeric data in the reference; a later update spins indefinitely, consuming CPU and hanging the request or job.

The record

CVE
CVE-2026-54904
Published
Jun 24, 2026
Updated
Jun 24, 2026
Vendor
ruby-concurrency
Product
concurrent-ruby
Classifications
CWE-835, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.3.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ruby-concurrency · concurrent-rubyversion=< 1.3.7

Published CVSS scores

8.2GitHubCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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