9.8

CVE-2025-52856: qnap systems inc. viostor Improper Authentication

CVSS: 9.8v3.1CriticalAnalyzed
Published 29-08-2025Last modified 26-02-2026
Open JSON

Vulnerability summary

CVE-2025-52856 is a critical (CVSS 9.8) Improper Authentication vulnerability in qnap systems inc. viostor. EPSS estimates a 0.66% chance of exploitation in the next 30 days, higher than 50.5% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.8/10
010
Critical · v3.1 (NVD)
EPSS score
0.66%
0%100%
Low · +0.02 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 29-08-2025
    PublishedVulnerability first disclosed.
  2. 26-02-2026
    Last modifiedVulnerability information updated.

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

CVSS metrics

3 scores · 2 sources · 2 versions

EPSS trend

Probability

0.66%

Chance of exploitation in the next 30 days

Percentile

51%

Versus all other CVEs

30-day change

+0.02 pp

From 0.63% on 20-09-2026

20-09-202620-10-2026
EPSS score
0.66%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Qnap1 product
  • qvr≥ 5.1.0, < 5.1.6 | 5.1.6
Qnap systems inc.1 product
  • viostor≥ 5.1.0, < 5.1.6 build 20250621

2 vendors · 2 products

References

1 links