Critical Authentication Bypass Vulnerability in Anritsu Remote Spectrum Monitor
Summary
CISA ICS-CERT published advisory ICSA-26-090-01 disclosing CVE-2026-3356, a critical authentication bypass vulnerability (CVSS 9.8) affecting all versions of Anritsu Remote Spectrum Monitor models MS27100A, MS27101A, MS27102A, and MS27103A. The vendor has no plans to remediate the vulnerability, which allows unauthorized network attackers to access and manipulate the device management interface. CISA recommends network isolation and secure deployment practices as mitigation.
What changed
CISA disclosed a critical vulnerability (CVE-2026-3356) in Anritsu Remote Spectrum Monitor devices used across Communications, Defense Industrial Base, Emergency Services, and Transportation Systems sectors. The flaw (CWE-306: Missing Authentication for Critical Function) carries a CVSS score of 9.8 and affects all versions of four Anritsu models. Attackers with network access can alter operational settings, obtain sensitive signal data, or disrupt device availability. Anritsu, headquartered in Japan, has declined to issue a patch or fix.
Organizations using these devices must immediately isolate them from the internet and business networks, place them behind firewalls, and use VPNs if remote access is required. Since no vendor remediation is planned, operators should contact Anritsu Technical Support (1-800-267-4878) for specific guidance and consider the operational necessity of these devices given the unfixable vulnerability.
What to do next
- Immediately identify all Anritsu Remote Spectrum Monitor devices (MS27100A/01A/02A/03A) on the network
- Isolate affected devices from the internet and business networks using firewalls or air-gapping
- Evaluate network architecture to prevent unauthorized access and assess operational necessity of affected devices
Source document (simplified)
ICS Advisory
Anritsu Remote Spectrum Monitor
Release Date
March 31, 2026
Alert Code ICSA-26-090-01 Related topics: Industrial Control System Vulnerabilities, Industrial Control Systems View CSAF
Summary
Successful exploitation of this vulnerability could allow attackers with network access to alter operational settings, obtain sensitive signal data, or disrupt device availability.
The following versions of Anritsu Remote Spectrum Monitor are affected:
- Remote Spectrum Monitor MS27100A vers:all/* (CVE-2026-3356)
- Remote Spectrum Monitor MS27101A vers:all/* (CVE-2026-3356)
- Remote Spectrum Monitor MS27102A vers:all/* (CVE-2026-3356)
- Remote Spectrum Monitor MS27103A vers:all/* (CVE-2026-3356)
| CVSS | Vendor | Equipment | Vulnerabilities |
| --- | --- | --- | --- |
| v3 9.8 | Anritsu | Anritsu Remote Spectrum Monitor | Missing Authentication for Critical Function |
Background
- Critical Infrastructure Sectors: Communications, Defense Industrial Base, Emergency Services, Transportation Systems
- Countries/Areas Deployed: Worldwide
- Company Headquarters Location: Japan
Vulnerabilities
CVE-2026-3356
The MS27102A Remote Spectrum Monitor is vulnerable to an authentication bypass that allows unauthorized users to access and manipulate its management interface. Because the device provides no mechanism to enable or configure authentication, the issue is inherent to its design rather than a deployment error.
Affected Products
Anritsu Remote Spectrum Monitor
Vendor:
Anritsu Product Version:
Anritsu Remote Spectrum Monitor MS27100A: vers:all/, Anritsu Remote Spectrum Monitor MS27101A: vers:all/, Anritsu Remote Spectrum Monitor MS27102A: vers:all/, Anritsu Remote Spectrum Monitor MS27103A: vers:all/ Product Status:
known_affected
Remediations
Mitigation
Anritsu has no plans to fix this issue. Anritsu recommends that users deploy Remote Spectrum Monitor within secure network environments to mitigate potential risks.
Mitigation
Users can contact Anritsu Technical Support (1-800-267-4878) for more information.
Relevant CWE: CWE-306 Missing Authentication for Critical Function
Metrics
| CVSS Version | Base Score | Base Severity | Vector String |
| --- | --- | --- | --- |
| 3.1 | 9.8 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Acknowledgments
- Souvik Kandar reported this vulnerability to CISA
Legal Notice and Terms of Use
This product is provided subject to this Notification (https://www.cisa.gov/notification) and this Privacy & Use policy (https://www.cisa.gov/privacy-policy).
Recommended Practices
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability.
Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the Internet.
Locate control system networks and remote devices behind firewalls and isolating them from business networks.
When remote access is required, use more secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as the connected devices.
CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices on the ICS webpage on cisa.gov/ics. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.
Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.
No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time.
Revision History
- Initial Release Date: 2026-03-31
| Date | Revision | Summary |
| --- | --- | --- |
| 2026-03-31 | 1 | Initial Publication |
Legal Notice and Terms of Use
This product is provided subject to this Notification and this Privacy & Use policy.
Tags
Sector: Communications Sector, Defense Industrial Base Sector, Emergency Services Sector, Transportation Systems Sector Topics: Industrial Control System Vulnerabilities, Industrial Control Systems
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