Answer in brief
CVE-2026-54904 records a High severity (CVSS 8.2) vulnerability in concurrent-ruby: `AtomicReference#update` livelocks when the stored value is `Float::NAN`. The current sources do not mark it as known exploited. The current feed maps ruby-concurrency/concurrent-ruby (generic), concurrent-ruby (rubygems), concurrent-ruby (rubygems). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 8.2. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps ruby-concurrency/concurrent-ruby (generic), concurrent-ruby (rubygems), concurrent-ruby (rubygems). Check affected ranges and fixed versions before updating.
| Product | Affected versions | Fixed versions |
|---|---|---|
| cpe:2.3:a:rubyconcurrency:concurrent_ruby:*:*:*:*:*:ruby:*:* | Not reported | Not reported |
| Package | Affected range | Fixed version |
|---|---|---|
| ruby-concurrency/concurrent-rubygeneric | < 1.3.7 | Not reported |
| concurrent-rubyrubygems | <1.3.7 | 1.3.7 |
| concurrent-rubyrubygems | >=0 <1.3.7 | 1.3.7 |
Published upstream
Jun 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 10, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jun 19, 2026
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.
Quoted source text, attributed separately from HOL analysis.