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    3 vulnerabilities by ruby-concurrency

    CVE-2026-54906 (GCVE-0-2026-54906)

    Vulnerability from cvelistv5 – Published: 2026-06-24 15:46 – Updated: 2026-06-24 17:57
    VLAI
    Title
    concurrent-ruby: ReadWriteLock allows wrong-thread write release and stray read-release counter corruption
    Summary
    concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. This vulnerability is fixed in 1.3.7.
    Severity
    2.1 (Low)
    CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
    SSVC
    Exploitation: poc Automatable: no Technical Impact: partial
    CISA Coordinator (v2.0.3)
    CWE
    Assigner
    References
    Impacted products
    Show details on NVD website
    To clipboard 

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    CVE-2026-54904 (GCVE-0-2026-54904)

    Vulnerability from cvelistv5 – Published: 2026-06-24 15:44 – Updated: 2026-06-25 13:20
    VLAI
    Title
    concurrent-ruby: `AtomicReference#update` livelocks when the stored value is `Float::NAN`
    Summary
    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.
    Severity
    8.2 (High)
    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
    SSVC
    Exploitation: poc Automatable: no Technical Impact: partial
    CISA Coordinator (v2.0.3)
    CWE
    • CWE-835 - Loop with Unreachable Exit Condition ('Infinite Loop')
    Assigner
    References
    Impacted products
    Show details on NVD website
    To clipboard 

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    CVE-2026-54905 (GCVE-0-2026-54905)

    Vulnerability from cvelistv5 – Published: 2026-06-24 15:42 – Updated: 2026-06-24 16:41
    VLAI
    Title
    concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity
    Summary
    concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReentrantReadWriteLock can incorrectly grant a write lock after one thread acquires the read lock 32,768 times. The lock stores a thread's local read and write hold counts in one integer. The low 15 bits are used for the read hold count, and bit 15 is used as WRITE_LOCK_HELD. After 32,768 reentrant read acquisitions, the local read count crosses into the write-lock bit. try_write_lock then treats the thread as already holding a write lock and returns true without setting the global RUNNING_WRITER bit. This breaks the core mutual-exclusion guarantee: the caller is told it has a write lock, but other threads can still hold or acquire read locks at the same time. This vulnerability is fixed in 1.3.7.
    Severity
    2 (Low)
    CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N
    SSVC
    Exploitation: poc Automatable: no Technical Impact: partial
    CISA Coordinator (v2.0.3)
    CWE
    Assigner
    References
    Impacted products
    Show details on NVD website
    To clipboard 

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