CVE-2026-40539 PUBLISHED

Assigner: synology
Reserved: 14.04.2026 Published: 18.09.2026 Updated: 18.09.2026

An improper certificate validation vulnerability in Email API in Synology DiskStation Manager (DSM) before 7.2.1-69057-10, 7.2.2-72806-7 and 7.3.2-86009-2 allows man-in-the-middle attackers to read or write arbitrary files and conduct denial-of-service attacks.

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
CVSS Score: 7.1

Attack Vector	Adjacent Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	High
Privileges Required	None	Integrity Impact	High
User Interaction	Required	Availability Impact	High

CVSS 3.1

Product Status

Vendor	Synology
Product	DiskStation Manager (DSM)
Versions	Default: affected affected from 7.3 to 7.3.2-86009-2 (excl.) affected from 7.2.2 to 7.2.2-72806-7 (excl.) affected from 7.2.1 to 7.2.1-69057-10 (excl.) unknown from 0 to 7.2.1 (excl.)

Credits

Ben R of Interrupt Labs (https://www.interruptlabs.co.uk) finder

References

Synology-SA-26:06 DSM

Problem Types

Improper Certificate Validation CWE