DiskStation Manager (DSM): Improper Certificate Validation
CVE-2026-40539 is a high-severity improper certificate validation vulnerability in DiskStation Manager (DSM) from Synology, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited from the same local network by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. The record lists versions 7.3.2-86009-2, 7.2.2-72806-7, 7.2.1-69057-10 as the first without the flaw, so updating DiskStation Manager (DSM) to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.12% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update DiskStation Manager (DSM) to 7.3.2-86009-2 or 7.2.2-72806-7 or 7.2.1-69057-10, whichever matches your release line, or a later version.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Synology | DiskStation Manager (DSM) | 7.3 up to, but not including, 7.3.2-86009-2; 7.2.2 up to, but not including, 7.2.2-72806-7; 7.2.1 up to, but not including, 7.2.1-69057-10 | 7.3.2-86009-2, 7.2.2-72806-7, 7.2.1-69057-10 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- AdjacentThe attacker must be on the same local network segment.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (synology.com).
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Certificate Validation
The product does not validate, or incorrectly validates, a certificate.
How developers prevent this class of flaw
- Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
- If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
More Improper Certificate Validation vulnerabilities (CWE-295)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
References
Other references
Other vulnerabilities in DiskStation Manager (DSM)
- 8.6 High severity
- 8.1 High severity
- 9.8 Critical severity
- 7.2 High severity
- 8.8 High severity
- 8.1 High severity
Recent Improper Certificate Validation vulnerabilities
- 7.4 High severity
- 8.3 High severity
- 7.7 High severity
- 8.3 High severity
- 8.1 High severity
- 9.1 Critical severity
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