---
id: "CVE-2026-86413"
kind: "vulnerability"
aliases: ["CVE-2026-86413"]
title: "curl: Negotiate credentials forwarded to unrelated origin on redirect"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["curl", "kerberos", "libcurl", "package", "self-hosted"]
not_affected_if: ["no-negotiate-auth", "no-redirect-following"]
published_at: "2026-10-20T20:17:25+00:00"
first_seen_at: "2026-10-23T21:57:21+00:00"
updated_at: "2026-10-25T05:04:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-86413", "first_seen_at": "2026-10-23T21:57:21+00:00"}]
---

# curl: Negotiate credentials forwarded to unrelated origin on redirect

When curl uses an ambient user for Negotiate authentication and follows redirects, it can send its credential details to a second, unrelated origin that the redirect points to. An attacker who controls a redirect target can receive those credentials.

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

## How to check

- Run `curl --version` and compare against the fixed release listed in the advisory, which the sources do not state
- Look for scripts or services that call curl with `--negotiate` or `--location` against hosts you do not control

## Fix

- Upgrade curl to a release that includes the fix for CVE-2026-86413; the exact version is unknown from the sources
- Until upgraded, avoid combining Negotiate authentication with following redirects to untrusted hosts

## Timeline

- 2026-10-23T21:57:21+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-86413

## From the sources

When using an *ambient user* in a first transfer doing Negotiate
authentication and asked to follow redirects, curl could pass on its
credential details to an unrelated second origin when asked to redirect there.

---

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