CVE-2026-54904
Description
A flaw was found in concurrent-ruby. A remote attacker could exploit a vulnerability in the Concurrent::AtomicReference#update method, which can enter a permanent busy retry loop. This occurs when the current value is a special 'Not a Number' (Float::NAN) floating-point value, causing the method to repeatedly attempt an operation without success. This can lead to a Denial of Service (DoS), where the affected application experiences CPU exhaustion or becomes unresponsive.
Statement
The issue arises when the AtomicReference#update method encounters a Float::NAN value, leading to an infinite retry loop and potential CPU exhaustion. The vulnerable AtomicReference#update method is not used with externally-controlled (e.g: Float::NAN) values - thus exploitation is not possible.
Mitigation
The vulnerable `AtomicReference#update` code path is not exercised with externally-derived numeric values, making exploitation not possible in this context.
Updating to concurrent-ruby 1.3.7 when available in upstream dependencies will fully resolve this issue.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.9 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Amplification
An infinite loop will cause unexpected consumption of resources, such as CPU cycles or memory. The software's operation may slow down, or cause a long time to respond.
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