vulnerability / NVI-00015218 / Revision 1
Concurrent Ruby : `AtomicReference#update` livelocks when the stored value is `Float::NAN`
GitHub lists this reviewed advisory for concurrent-ruby. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
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7.5 high
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
concurrent-ruby
source listed< 1.3.7
### Summary `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. - 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. ### Version Software: concurrent-ruby Version: 1.3.6 Commit: 7a1b78941c081106c20a9ca0144ac73a48d254ab ### Details `AtomicReference#update` retries until `compare_and_set` returns true: ```ruby def update true until compare_and_set(old_value = get, new_value = yield(old_value)) new_value end ``` For numeric expected values, `compare_and_set` uses numeric equality before attempting the underlying atomic compare-and-set: ```ruby def compare_and_set(ol
03 / Response
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- investigate
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04 / Limits
What this report cannot establish
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05 / Provenance
Sources you can inspect
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- GHSA-h8w8-99g7-qmvj ↗
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- Revision 1 ·
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