Improper Certificate Validation in DiskStation Manager (DSM) - CVE-2026-40539
Published: April 16, 2026
Vulnerability identifier: #VU126272
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-40539
CWE-ID: CWE-295
Exploitation vector: Adjecent network
Exploit availability:
No public exploit available
Vendor: Synology Inc.
Affected software:
DiskStation Manager (DSM)
DiskStation Manager (DSM)
Detailed vulnerability description
The vulnerability allows a remote attacker to read or write arbitrary files and cause a denial of service.
The vulnerability exists due to improper certificate validation in DSM when establishing adjacent-network connections. A remote attacker can perform a man-in-the-middle attack to read or write arbitrary files and cause a denial of service.
User interaction is required.
How to mitigate CVE-2026-40539
Install security update from vendor's website.