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CVE-2026-54904— concurrent-ruby: `AtomicReference#update` livelocks when the stored value is `Float::NAN`

Quick assessment

Affected
ruby-concurrency concurrent-ruby
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

ruby-concurrency Concurrent Ruby是ruby-concurrency组织开源的一款并发编程工具库。 concurrent-ruby 1.3.7之前版本存在资源管理错误漏洞，该漏洞源于当Concurrent::AtomicReference#update的当前值为Float::NAN时，易进入永久忙重试循环，导致CPU耗尽或永久请求/作业挂起。以下版本受到影响：1.3.7之前版本。

CVSS 8.2 · High EPSS 0.67% · P50

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
ruby-concurrency concurrent-ruby < 1.3.7 affected
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I. Basic Information for CVE-2026-54904

Vulnerability Information
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Vulnerability Title
concurrent-ruby: `AtomicReference#update` livelocks when the stored value is `Float::NAN`
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5
Vulnerability Title
ruby-concurrency concurrent-ruby 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
ruby-concurrency Concurrent Ruby是ruby-concurrency组织开源的一款并发编程工具库。 concurrent-ruby 1.3.7之前版本存在资源管理错误漏洞，该漏洞源于当Concurrent::AtomicReference#update的当前值为Float::NAN时，易进入永久忙重试循环，导致CPU耗尽或永久请求/作业挂起。以下版本受到影响：1.3.7之前版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
ruby-concurrency concurrent-ruby < 1.3.7 -

II. Public POCs for CVE-2026-54904

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 6211 chars
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III. Intelligence Information for CVE-2026-54904

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Patches & Fixes for CVE-2026-54904 (1)

Vendor Advisories for CVE-2026-54904 (1)

Vendor Pages for CVE-2026-54904 (1)

Other References for CVE-2026-54904 (1)

Same Patch Batch · ruby-concurrency · 2026-06-24 · 3 CVEs total

CVE-2026-54906 concurrent-ruby: ReadWriteLock allows wrong-thread write release and stray read-release co
CVE-2026-54905 concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without

IV. Related Vulnerabilities

Same product: concurrent-ruby
Same vendor: ruby-concurrency
Same weakness: CWE-835

V. Comments for CVE-2026-54904

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