Notes Station 3 XSS Vulnerability Fixed in 3.9.12
CVE-2026-39991 Published on October 15, 2026
Stored Cross-Site Scripting (XSS) in Note Station file upload functionality
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
Vulnerability Analysis
CVE-2026-39991 can be exploited with network access. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
What is a XSS Vulnerability?
The software does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
CVE-2026-39991 has been classified to as a XSS vulnerability or weakness.
Products Associated with CVE-2026-39991
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Affected Versions
QNAP Systems Inc. Notes Station 3:- Version 3.9.x and below 3.9.12 is affected.