Is CVE-2026-86411 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-86411 being exploited in the wild.

How severe is CVE-2026-86411?

Informational severity, published 20 October 2026.

Is there a fix for CVE-2026-86411?

Yes: fixed in curl 8.22.0. Until then: Do not use client certificates for FTP transfers, or upgrade to curl 8.22.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-86411 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-86411?

Check whether you run Curl at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-86411: curl FTP connection reuse inherits client certificate

CVE-2026-86411 · Severity: info · Published 2026-10-20

curl is a widely-used library and tool for transferring files over the network using protocols like FTP. When reusing FTP connections across different application components or requests, curl can inadvertently allow a second connection to inherit the client certificate authentication of a previous connection. This means an unauthorized user could gain access under a legitimate client's identity without providing their own credentials.

Technologies: Curl. Vendors: Curl.

Quick answers

Is CVE-2026-86411 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-86411 being exploited in the wild.
How severe is CVE-2026-86411?: Informational severity, published 20 October 2026.
Which products and versions are affected?: Curl 8.21.0.
Is there a fix for CVE-2026-86411?: Yes: fixed in curl 8.22.0. Until then: Do not use client certificates for FTP transfers, or upgrade to curl 8.22.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-86411 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-86411?: Check whether you run Curl at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: curl 8.22.0

Do not use client certificates for FTP transfers, or upgrade to curl 8.22.0 or later.

Technical details

An ftp:// transfer configured with CURLUSESSL_NONE can reuse a pooled FTP control connection from a previous easy handle that was 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 (CWE-488: Exposure of Data Element to Wrong Session).

Affected products

curl curl 8.21.0

Timeline

2026-08-27: disclosed
2026-09-02: patched
2026-10-14: advisory

References

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