CVE-2026-54906

2.1 LOW 0.2% exploit odds Fix listed Other

What it is

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.

At a glance

Exploitability: Can be exploited locally on the machine without logging in. Limited direct impact.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-06-24 17:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-25 22:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 2.1 LOW (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-06-24 17:17 UTC
Last modified: 2026-10-25 22:10 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-414
Record status: Analyzed

Affected

Rubyconcurrency Concurrent Ruby < 1.3.7

Attack profile CVSS 4.0 · 2.1

Attack vector: Local
Complexity: High
Attack requirements: None
Privileges needed: None
User interaction: None
Confidentiality: None
Integrity: Low
Availability: Low

Raw vector

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-54906.md and follow it. Check whether this project is affected by CVE-2026-54906. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record