CVE-2026-39991 PUBLISHED

Stored Cross-Site Scripting (XSS) in Note Station file upload functionality

Assigner: qnap
Reserved: 08.04.2026 Published: 15.10.2026 Updated: 15.10.2026

A cross-site scripting (XSS) vulnerability has been reported to affect Notes Station 3. If a remote attacker gains a user account, they can then exploit the vulnerability to inject malicious code.

We have already fixed the vulnerability in the following version: Notes Station 3 3.9.12 and later

Metrics

CVSS 4.0

CVSS Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
CVSS Score: 4.8

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	Low
Attack Complexity	Low	Integrity	None	Integrity	Low
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	Low
User Interaction	Active

CVSS 4.0

Product Status

Vendor	QNAP Systems Inc.
Product	Notes Station 3
Versions	Default: unaffected affected from 3.9.x to 3.9.12 (excl.)

Solutions

We have already fixed the vulnerability in the following version: Notes Station 3 3.9.12 and later

Credits

Ahmad Mamdouh finder

References

https://www.qnap.com/en/app-release-notes?keyword=Notes%20Station%203&app=NotesStation3&product-line=nas

Problem Types

CWE-79 CWE

Impacts

CAPEC-592