---
title: "CVE-2026-40539: Synology DiskStation Manager - Improper Certificate Validation"
description: "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."
url: https://panop.io/threat-heartbeat/CVE-2026-40539/
---

# 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 ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-40539)

## 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](https://cwe.mitre.org/data/definitions/295.html)

## 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

- [https://nvd.nist.gov/vuln/detail/CVE-2026-40539](https://nvd.nist.gov/vuln/detail/CVE-2026-40539)
- [https://www.synology.com/en-global/security/advisory/Synology\_SA\_26\_06](https://www.synology.com/en-global/security/advisory/Synology_SA_26_06)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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