CVE-2026-39991 Stored Cross-Site Scripting (XSS) in Note Station file upload functionality
Remote attackers with user accounts can inject malicious scripts via file uploads in QNAP Notes Station, potentially compromising other users.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-39991?
CVE-2026-39991 is a medium-severity cross-site scripting vulnerability in QNAP Systems Inc. Notes Station 3, published on 15 Oct 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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
Weakness: CWE-79
Which versions are affected by CVE-2026-39991?
How do I fix CVE-2026-39991?
No fix has been published for CVE-2026-39991 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-39991 being exploited?
There is no known exploitation of CVE-2026-39991 in the wild and no public exploit code.
Sources
Also known as GHSA-gm69-cjmx-9r3x.