VioStor: Improper Authentication
CVE-2025-52856 is a critical-severity improper authentication vulnerability in VioStor from QNAP, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 5.1.6 build 20250621 as the first without the flaw, so updating VioStor to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.66% chance of exploitation within 30 days, higher than 52% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update VioStor to 5.1.6 build 20250621 or a later version.
- Update Qvr to 5.1.6 or a later version.
- Read the advisory on qnap.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| QNAP | VioStor | 5.1.0 up to, but not including, 5.1.6 build 20250621 | 5.1.6 build 20250621 |
| QNAP | Qvr | 5.1.0 up to, but not including, 5.1.6; 5.1.6 | 5.1.6 |
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
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- 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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA (qnapsecurity.com.tw) |
| CVSS 3.1 | 9.8 | Critical | NVD |
Official description
An improper authentication vulnerability has been reported to affect VioStor. If a remote attacker, they can then exploit the vulnerability to compromise the security of the system. We have already fixed the vulnerability in the following version: VioStor 5.1.6 build 20250621 and later
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Authentication
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
How developers prevent this class of flaw
- Use an authentication framework or library such as the OWASP ESAPI Authentication feature.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in VioStor
- 7.0 High severity
Recent Improper Authentication vulnerabilities
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 9.8 Critical severity
- 7.8 High severity
- 7.5 High severity
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