---
schema_version: '1.0'
id: security-20260705-72944d
url: https://osv.dev/vulnerability/CURL-CVE-2026-1965
url_hash: 72944d028885a32c05f5a39f09a0709a02c48461db24f4ccd0828d4c9d04d05d
canonical_url: https://osv.dev/vulnerability/CURL-CVE-2026-1965
source: osv:osv
category: security/library
category_raw: cve/library
region: null
tags:
- cve
- CVE-2026-1965
- CURL-CVE-2026-1965
- severity:Medium
- https://github.com/curl/curl
- GIT
lang: en
published_at: '2026-03-11T08:00:00Z'
fetched_at: '2026-07-05T15:34:34Z'
updated_at: '2026-07-05T15:37:46Z'
status: published
content_hash: 387fdb7f693a929a5b2b65abf83a6c532209e7e5411c04587aa8085e9b2881e3
license_note: full
summary: bad reuse of HTTP Negotiate connection
summary_source: rss
summary_en: bad reuse of HTTP Negotiate connection
entities:
- name: GitHub
  type: organization
- name: bad_engineering_decisions
  type: concept
- name: HTTP Request-Response Structure
  type: concept
key_facts: []
related: []
related_auto:
- name: Intent-centric Protocol
  type: UNKNOWN
  weight: 2.0
- name: Anonymous
  type: organization
  weight: 1.0
- name: AirPods
  type: artifact
  weight: 1.0
- name: Claude Code
  type: artifact
  weight: 1.0
- name: セッション漏洩
  type: event
  weight: 1.0
title: 'CVE-2026-1965: bad reuse of HTTP Negotiate connection'
---

# CVE-2026-1965: bad reuse of HTTP Negotiate connection

## TL;DR
bad reuse of HTTP Negotiate connection

## Key Points
- cve / CVE-2026-1965 / CURL-CVE-2026-1965 / severity:Medium / https://github.com/curl/curl / GIT

## Details
**Severity:** Medium
**Advisory:** CURL-CVE-2026-1965 (CVE-2026-1965)

**Affected (your watchlist):**
- `GIT:https://github.com/curl/curl` curl-8_9_1 → no fixed version listed [mac]

**Details:**
libcurl can in some circumstances reuse the wrong connection when asked to do
an Negotiate-authenticated HTTP or HTTPS request.

libcurl features a pool of recent connections so that subsequent requests can
reuse an existing connection to avoid overhead.

When reusing a connection a range of criterion must first be met. Due to a
logical error in the code, a request that was issued by an application could
wrongfully reuse an existing connection to the same server that was
authenticated using different credentials. One underlying reason being that
Negotiate sometimes authenticates *connections* and not *requests*, contrary
to how HTTP is designed to work.

An application that allows Negotiate authentication to a server (that responds
wanting Negotiate) with `user1:password1` and then does another operation to
the same server also using Negotiate but with `user2:password2` (while the
previous connection is still alive) - the second request wrongly reused the
same connection and since it then sees that the Negotiate negotiation is
already made, it sends the request over that connection thinking it uses
the user2 credentials when it is in fact still using the connection
authenticated for user1...

The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`.

Applications can disable libcurl's reuse of connections and thus mitigate this
problem, by using one of the following libcurl options to alter how
connections are or are not reused: `CURLOPT_FRESH_CONNECT`,
`CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the
curl_multi API).

_Data: OSV.dev (upstream: osv) — https://osv.dev/vulnerability/CURL-CVE-2026-1965_

## Source
元記事: [CVE-2026-1965: bad reuse of HTTP Negotiate connection](https://osv.dev/vulnerability/CURL-CVE-2026-1965) — published 2026-03-11T08:00:00Z