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.

Metrics

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00259.

Exploitation poc

Automatable yes

Technical Impact total

Affected Vendors & Products

Vendors Products
Curl Subscribe
Curl Subscribe

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

Vendors Products
Curl Subscribe
Curl Subscribe
Advisories

No advisories yet.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://curl.se/docs/CVE-2026-19931.html cve-icon cve-icon
https://curl.se/docs/CVE-2026-19931.json cve-icon cve-icon
https://hackerone.com/reports/3923520 cve-icon cve-icon cve-icon
History

Tue, 08 Sep 2026 19:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-269
CWE-668

Tue, 08 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-488
Metrics cvssV3_1

{'score': 9.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Sun, 06 Sep 2026 19:45:00 +0000

Type Values Removed Values Added
First Time appeared Curl
Curl curl
Weaknesses CWE-269
CWE-668
Vendors & Products Curl
Curl curl

Sun, 06 Sep 2026 18:00:00 +0000

Type Values Removed Values Added
Description 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.
Title Negotiate ambient user conn reuse
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: curl

Published:

Updated: 2026-09-08T15:42:43.125Z

Reserved: 2026-08-15T10:35:02.789Z

Link: CVE-2026-19931

cve-icon Vulnrichment

Updated: 2026-09-08T15:42:38.212Z

cve-icon NVD

Status : Undergoing Analysis

Published: 2026-09-06T18:17:20.733

Modified: 2026-09-08T16:18:07.080

Link: CVE-2026-19931

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-08T18:45:05Z

Weaknesses