CVE-2026-19931

CRITICAL

A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is done using empty credentials. This can make user B's request get sent over user A's previously authenticated connection.

CVSS v3.1 Score

9.8
CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Published: 9/6/2026Modified: 9/11/2026

Related Intelligence (1)

CRITICALRansomware

Patch Tuesday - September 2026

Microsoft is publishing 974 own-product vulnerabilities on September 2026 Patch Tuesday , including 723 vulnerabilities in Windows. Along with Microsoft fixes for 25 non-Microsoft CVEs, that brings the total number of vulnerabilities on the table today to 999. Whether this is the biggest Patch Tuesday ever depends on how we count, but this is by far the most CVEs that Microsoft has ever published

CVE-2026-85880CVE-2026-81963
Rapid7

References (4)

https://curl.se/docs/CVE-2026-19931.htmlPatchVendor Advisoryhttps://curl.se/docs/CVE-2026-19931.jsonVendor Advisoryhttps://hackerone.com/reports/3923520ExploitMitigationhttps://hackerone.com/reports/3923520ExploitMitigation