CVE-2026-40539 Synology DiskStation Manager - Improper Certificate Validation

Synology DiskStation Manager (DSM) < 7.2.1-69057-10, 7.2.2-72806-7, and 7.3.2-86009-2 contains an improper certificate validation vulnerability in Email API, letting man-in-the-middle attackers read or write arbitrary files and cause denial of service, exploit requires man-in-the-middle position.

CVSS base score 7.1 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.12% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
Improper Certificate Validation
Impact
File System Read, File System Write, Denial Of Service, Man In The Middle
CVSS vector
CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Published
18 September 2026
Updated
15 October 2026
Weakness
CWE-295

Vendor fix

Update to versions 7.2.1-69057-10, 7.2.2-72806-7, 7.3.2-86009-2 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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