---
id: "CVE-2026-86411"
kind: "vulnerability"
aliases: ["CVE-2026-86411"]
title: "curl: pooled FTP connection reuse keeps a prior client certificate identity"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["c", "client-certificates", "ftp", "libcurl", "package", "php", "python"]
not_affected_if: ["no-client-certificates", "no-ftp", "single-handle"]
published_at: "2026-10-20T20:17:25+00:00"
first_seen_at: "2026-10-23T21:57:21+00:00"
updated_at: "2026-10-25T05:04:36+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-86411", "first_seen_at": "2026-10-23T21:57:21+00:00"}]
---

# curl: pooled FTP connection reuse keeps a prior client certificate identity

An ftp:// transfer set to CURLUSESSL_NONE can reuse a pooled FTP control connection that an earlier handle upgraded with STARTTLS and authenticated with a client certificate. The reused connection carries that earlier certificate identity, so the server authorizes the second transfer under credentials it never presented.

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

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-23T21:57:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-86411

## From the sources

An `ftp://` transfer configured with `CURLUSESSL_NONE` can reuse a pooled FTP
control connection that a previous easy handle upgraded with `STARTTLS` and
authenticated using a client certificate. The second handle performs neither a
new TLS handshake nor a new FTP login, so the server continues to authorize it
under the first handle's certificate identity.

---

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