CVE-2026-54906: concurrent-ruby is a modern concurrency tools for Ruby

Q: How do I fix CVE-2026-54906?

concurrent ruby: upgrade to 1.3.7. Exact commands for each OS are on this page.

Q: Is CVE-2026-54906 being exploited?

CVE-2026-54906 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-54906 affect?

CVE-2026-54906 affects concurrent ruby. Severity is critical (CVSS 9.8). 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 a

Q: How urgent is CVE-2026-54906?

Priority 41/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-54906 is a critical-severity flaw (CVSS 9.8) affecting concurrent ruby. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 count

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 95%)
CISA exploited list	No
Weakness	CWE-414, CWE-667
Published	2026-06-24
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: rubyconcurrency

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-24 17:17 UTCPublished CVE record published
2026-10-25 22:10 UTCUpdated Record last modified

rubyconcurrency concurrent ruby UPGRADE

Affected: < 1.3.7

Fixed in: 1.3.7

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy concurrent-ruby || rpm -q concurrent-ruby || concurrent-ruby --version

2. UPGRADE to 1.3.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade concurrent-ruby

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade concurrent-ruby

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-54906?

concurrent ruby: upgrade to 1.3.7. Exact commands for each OS are on this page.

Is CVE-2026-54906 being exploited?

CVE-2026-54906 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-54906 affect?

CVE-2026-54906 affects concurrent ruby. Severity is critical (CVSS 9.8). 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 a

How urgent is CVE-2026-54906?

Priority 41/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Ruby vulnerabilities

Related CVEs

CVE-2026-54904 HIGH 7.5 UPGRADE concurrent-ruby is a modern concurrency tools for Ruby
CVE-2026-54905 MEDIUM 5.5 UPGRADE concurrent-ruby is a modern concurrency tools for Ruby

References

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