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VulnerabilityPublished

CVE-2026-54905: concurrent-ruby · Wrap-around Error

Affects concurrent-rubySource CVE Database V5

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Not known to be exploited · CVSS 2.0 Low : upgrade to 1.3.7 when convenient.

Data as of 5 Nov 2026, 00:01 UTC

CVSS 4.0 base score
2.0Low
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 4% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.3.7
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 24 Jun 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade concurrent-ruby to 1.3.7.

Affected software

ProductAffectedFixed in
ruby-concurrencyconcurrent-rubyAffected
  • <1.3.7
Fixed in
  • 1.3.7
RubyGemsconcurrent-rubypkg:gem/concurrent-rubyOther threatsAffected
  • <1.3.7
Fixed in
  • 1.3.7

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade concurrent-ruby to version 1.3.7 or later, where this vulnerability is fixed. No other official remediation or temporary fix is indicated. Patch status is confirmed by the version fix information.

Description

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.

References

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