7.1High
CVE-2026-40539
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.
What this means for your business
- An attacker can use it from inside the same network, without a login, but only after tricking someone into an action such as opening a file or a link.
- FIRST's prediction model gives it a less than 0.1% chance of attack attempts being seen in the next 30 days, ranking above 0% of all known flaws.
What to do
- 1Ask your IT team or provider whether any of your systems use the affected product.
- 2If you do, follow the vendor's guidance. No patch reference has been published yet.
Not sure if your company is exposed?
Fastnexa’s certified penetration testers can check whether attackers could use this flaw, or others like it, against your websites, apps and network. The full test is free for our first 10 founding clients until 31 December 2026.
Scoring
- CVSS
- 7.1 (v3.1)
- Vector
CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H- Weakness
- CWE-295
- Assigned by
- security@synology.com
Dates
- Published
- 2026-09-18
- Last modified
- 2026-09-18
- Sources
- NVD