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Vulnerabilities

Vulnerability · CVE-2026-39991

A cross-site scripting (XSS) vulnerability has been reported to affect Notes Station 3.

Published Oct 15, 2026 · catalog updated Oct 15, 2026 · QNAP Systems Inc. Notes Station 3

Check if you run it

No confirmed exploitation is on record for CVE-2026-39991. EPSS is 0.29%. Act only if a listed version of QNAP Systems Inc. Notes Station 3 is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium4.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.29%
Remediation
Not established
Affected products
vendor QNAP Systems Inc. Notes Station 3

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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor QNAP Systems Inc. Notes Station 3version unspecified

How to fix CVE-2026-39991

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-39991. EPSS is 0.29%. Act only if a listed version of QNAP Systems Inc. Notes Station 3 is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.29%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

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.

  1. 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

  2. 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

  3. 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

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 0.3%

    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

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.