Vulnerability · Published Oct 20, 2026 · Assigned by curl
CVE-2026-86411FTP connection reuse inherits client-certificate
Critical 9.1
In plain English
A critical-severity security flaw in curl from curl. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.23 | curl | 8.23.0-r0 | ALPINE-CVE-2026-86411 |
| Alpine:v3.24 | curl | 8.23.0-r0 | ALPINE-CVE-2026-86411 |
| Debian:14 | curl | 8.22.0-1 | DEBIAN-CVE-2026-86411 |
Affected products (as reported)
Weakness: CWE-488 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N