CVE-2026-109681: The FTP client trusts the server's PASV response IP:port without validation against the control connection target
CVE-2026-109681 analysis covering impact, affected products, versions, remediation, and cross-checked defender guidance.
CVE-2026-109681 is a vulnerability published by NVD on 10/21/2026.
What happened
The FTP client trusts the server's PASV response IP:port without validation against the control connection target. A rogue FTP server can specify any IP:port in the 227 Passive Mode response, causing the operator's machine to open a TCP connection to an arbitrary host.
Affected products and versions
- NVD has not published a normalized affected-product configuration yet.
Severity and weakness
CVSS: MEDIUM 4.7. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N.
Weaknesses: CWE-918.
Known exploitation
No CISA KEV entry is currently attached to the NVD record.
What defenders should do
- Identify whether the affected product and version range exists in production.
- Review vendor advisories and release notes before change windows.
- Patch, upgrade, disable the vulnerable component, or apply vendor mitigations.
- Verify the running version after deployment, not only the package inventory.
Official and supporting references
- No vendor advisory tagged by NVD at draft time.