---
id: "CVE-2026-109681"
kind: "vulnerability"
aliases: ["CVE-2026-109681"]
title: "FTP client trusts server PASV reply, can open connections to arbitrary hosts"
severity: "medium"
cvss: 4.7
epss: 0.00201
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["ftp", "other", "self-hosted"]
not_affected_if: []
published_at: "2026-10-21T00:17:17+00:00"
first_seen_at: "2026-10-23T21:57:27+00:00"
updated_at: "2026-10-25T04:34:57+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109681", "first_seen_at": "2026-10-23T21:57:27+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-109681", "first_seen_at": "2026-10-24T13:15:55+00:00"}]
---

# FTP client trusts server PASV reply, can open connections to arbitrary hosts

The FTP client accepts the IP address and port in a server's 227 Passive Mode response without checking them against the server it is connected to. A rogue FTP server can therefore make the client open a TCP connection to any host and port the attacker chooses.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-23T21:57:27+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-109681
- 2026-10-24T13:15:55+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-109681

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_