CVE-2026-40538 Synology CVE debrief

Who should care

System administrators and security teams responsible for Synology DiskStation Manager (DSM) deployments should assess exposure and apply patches or mitigations as needed to prevent potential exploitation. This includes reviewing and updating incident response plans to address potential exploitation and implementing additional security measures to prevent brute-force attacks.

Why it matters

CVE-2026-40538 is a vulnerability in Synology DiskStation Manager (DSM) that allows remote attackers to read limited files via brute-force attacks. System administrators and security teams should assess exposure and apply patches or mitigations as needed.

• Verify and apply patches for Synology DiskStation Manager (DSM) versions before 7.2.1-69057-10, 7.2.2-72806-7, and 7.3.2-86009-2 to prevent potential exploitation
• Implement additional security measures to prevent brute-force attacks
• Review and update incident response plans to address potential exploitation

Technical summary

The vulnerability is caused by improper restriction of excessive authentication attempts in Synology DiskStation Manager (DSM) versions before 7.2.1-69057-10, 7.2.2-72806-7, and 7.3.2-86009-2. This allows remote attackers to read limited files via brute-force attacks. The vulnerability has a CVSS score of 3.7 and is considered low severity. System administrators and security teams should assess exposure and apply patches or mitigations as needed to prevent potential exploitation. Additional security measures should be implemented to prevent brute-force attacks.

Defensive priority

Verify and apply patches for Synology DiskStation Manager (DSM) versions before 7.2.1-69057-10, 7.2.2-72806-7, and 7.3.2-86009-2.

Recommended defensive actions

• Verify and apply patches for Synology DiskStation Manager (DSM) versions before 7.2.1-69057-10, 7.2.2-72806-7, and 7.3.2-86009-2
• Monitor authentication attempts and implement additional security measures to prevent brute-force attacks
• Review and update incident response plans to address potential exploitation
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and NVD entry provide limited information about the vulnerability. Further verification is required to determine the full scope of affected systems and potential impact. The Synology security advisory indicates that the vulnerability allows remote attackers to read limited files via brute-force attacks. Additional security measures should be implemented to prevent such attacks. The CVE record was published on 2026-09-18T09:16:41.307Z and has not been modified since then.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.