CVE-2026-19931 - Vulnerability Details - OpenCVE

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.

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.

Exploitation poc

Automatable yes

Technical Impact total

Vendors	Products
Curl	Curl

No data.

No data.

References

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

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		https://curl.se/docs/CVE-2026-19931.html https://curl.se/docs/CVE-2026-19931.json https://hackerone.com/reports/3923520

MITRE

Status: PUBLISHED

Assigner: curl

Published: 2026-09-06T17:47:43.523Z

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

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

Link: CVE-2026-19931

Vulnrichment

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

NVD

Status : Undergoing Analysis

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

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

Link: CVE-2026-19931

Redhat

No data.

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This can make user B's request get sent over user A's\npreviously authenticated connection."}], "problemTypes": [{"descriptions": [{"lang": "en", "description": "CWE-488 Exposure of Data Element to Wrong Session"}]}], "providerMetadata": {"orgId": "2499f714-1537-4658-8207-48ae4bb9eae9", "shortName": "curl", "dateUpdated": "2026-09-06T17:47:43.523Z"}}}, "cveMetadata": {"cveId": "CVE-2026-19931", "state": "PUBLISHED", "dateUpdated": "2026-09-08T15:42:43.125Z", "dateReserved": "2026-08-15T10:35:02.789Z", "assignerOrgId": "2499f714-1537-4658-8207-48ae4bb9eae9", "datePublished": "2026-09-06T17:47:43.523Z", "assignerShortName": "curl"}, "dataVersion": "5.2"}

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This can make user B's request get sent over user A's\npreviously authenticated connection."}], "id": "CVE-2026-19931", "lastModified": "2026-09-08T16:18:07.080", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-19931", "options": [{"exploitation": "poc"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-09-08T15:42:15.881334Z", "version": "2.0.3"}}]}, "published": "2026-09-06T18:17:20.733", "references": [{"source": "2499f714-1537-4658-8207-48ae4bb9eae9", "url": "https://curl.se/docs/CVE-2026-19931.html"}, {"source": "2499f714-1537-4658-8207-48ae4bb9eae9", "url": "https://curl.se/docs/CVE-2026-19931.json"}, {"source": "2499f714-1537-4658-8207-48ae4bb9eae9", "url": "https://hackerone.com/reports/3923520"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "url": "https://hackerone.com/reports/3923520"}], "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9", "vulnStatus": "Undergoing Analysis", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-488"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}