CVE-2026-40538 Synology CVE debrief

Who should care

Defenders responsible for Synology DiskStation Manager (DSM) systems should assess exposure and implement compensating controls to prevent brute-force attacks. This includes verifying exposure by checking Synology DiskStation Manager (DSM) versions and configurations, implementing compensating controls such as rate limiting and IP blocking, and monitoring system logs for suspicious activity.

Why it matters

CVE-2026-40538 is a low-severity vulnerability in Synology DiskStation Manager (DSM) that allows remote attackers to read limited files via brute-force attacks. Defenders responsible for DSM systems should assess exposure and implement compensating controls.

• Verify exposure and implement compensating controls to prevent brute-force attacks.
• Monitor system logs for suspicious activity and implement additional security measures as needed.
• Remediation priority is low due to the CVSS score of 3.7 (LOW).

Technical summary

The vulnerability exists in the Auto block feature of Synology DiskStation Manager (DSM) and allows remote attackers to read limited files via brute-force attacks. The CVSS score is 3.7 (LOW). This vulnerability affects Synology DiskStation Manager (DSM) systems, specifically versions before 7.2.1-69057-10, 7.2.2-72806-7, and 7.3.2-86009-2. The vulnerability is caused by an improper restriction of excessive authentication attempts, which allows remote attackers to read limited files via brute-force attacks. Defenders should prioritize verifying exposure and implementing compensating controls.

Defensive priority

Defenders should prioritize verifying exposure and implementing compensating controls, as the vulnerability allows remote attackers to read limited files via brute-force attacks.

Recommended defensive actions

• Verify exposure by checking Synology DiskStation Manager (DSM) versions and configurations.
• Implement compensating controls, such as rate limiting and IP blocking, to prevent brute-force attacks.
• Monitor system logs for suspicious activity and implement additional security measures as needed.
• 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.
• Track exceptions, retest remediated assets, and close the item only after evidence is documented.

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 remediation steps. The vulnerability exists in the Auto block feature of Synology DiskStation Manager (DSM) and allows remote attackers to read limited files via brute-force attacks. The CVSS score is 3.7 (LOW).

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.