CVE-2026-39991
A cross-site scripting (XSS) vulnerability has been reported to affect Notes Station 3.
Published Oct 15, 2026 · corrected/updated Oct 15, 2026 · QNAP Systems Inc. Notes Station 3 · evidence confidence high
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
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-39991 is a medium public vulnerability record for QNAP Systems Inc. Notes Station 3. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether QNAP Systems Inc. Notes Station 3 is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: QNAP Systems Inc. Notes Station 3. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 4.8, EPSS 0.5%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-79. Sources contributing to this record: circl, cve_org, epss, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Oct 15, 2026 · NIST NVD
Detected
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
Oct 15, 2026 · NIST NVD
Updated
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
Oct 15, 2026 · NIST NVD
Updated
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
Affected
- vendor QNAP Systems Inc. Notes Station 3version unspecified
Sources
- CIRCL Vulnerability LookupVulnerability recordCVE-2026-39991
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
vulnerability.circl.lu - CVE.orgVulnerability recordCVE-2026-39991
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-39991
30-day exploitation probability 0.5%
first.org - NIST NVDVulnerability recordCVE-2026-39991
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
nvd.nist.gov