---
id: CVE-2026-40539
title: >-
  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 de…
summary: >-
  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 de…
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H'
cwe:
  - CWE-295
vendor: Synology
product: DiskStation Manager (DSM)
affected:
  - diskstation_manager_dsm >= 7.3 < 7.3.2-86009-2
  - diskstation_manager_dsm >= 7.2.2 < 7.2.2-72806-7
  - diskstation_manager_dsm >= 7.2.1 < 7.2.1-69057-10
published: '2026-09-18'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T19:07:38.320'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-40539'
references:
  - url: 'https://www.synology.com/en-global/security/advisory/Synology_SA_26_06'
    label: security@synology.com
tags:
  - nvd
  - cve.org
epss: 0.00117
epssPercentile: 0.0149
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-09-18T10:39:51.196824Z'
ingestedAt: '2026-09-18T08:38:04.108Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.