Cyber Resilience

CVE-2026-54905

Rubyconcurrency Concurrent Ruby ≤ 1.3.7

Published
24 June 2026
Modified
26 June 2026
CVSS Score v4 2.0
Click a component to see what it means
Raw vectorCVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/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
EPSS Score 0.0011 1th percentile
Risk Priority 18 floored blend · peak EPSS

Summary

CVE-2026-54905 is a low-severity Wrap-around Error (CWE-128) vulnerability in Rubyconcurrency Concurrent Ruby. Its CVSS base score is 2.0 (Low).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

EU & UK References

No EU or UK CSIRT advisories indexed for this CVE.

Vulnerability Data

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…

more

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.

CWE(s)
CWE-128

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
T1687 Exploitation for Defense Impairment Defense Impairment
Adversaries may exploit vulnerabilities in security software, infrastructure, or defensive components to degrade, disable, or otherwise continue to impair their ability to prevent, detect, or respond to malicious activity.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-54906Same product: Rubyconcurrency Concurrent Ruby
CVE-2026-54904Same product: Rubyconcurrency Concurrent Ruby
CVE-2024-23981Shared CWE-128

Affected Assets

rubyconcurrency
concurrent ruby
≤ 1.3.7

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover wrap-around conditions through static analysis or test cases.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles include use of safe arithmetic constructs and bounded types that structurally avoid wrap-around.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly prevent wrap-around via safe arithmetic, bounds checks, and language features, but the control addresses many additional weakness classes.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect wrap-around errors through boundary and fuzz testing.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle includes input validation and bounds checking that can prevent wrap-around errors.

A.8.26 Application security requirements partial match
prevents

Application security requirements can mandate integer overflow protection and safe arithmetic.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include use of safe data types and overflow detection mechanisms.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly require avoidance of integer overflow and wrap-around conditions.

References