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CVE-2026-19931

Negotiate ambient user conn reuse

Published: Sep 6, 2026Updated: Sep 15, 2026 Sources: CVE List NVDCWE-488
9.8CRITICAL
NVD MITRE
EPSS Score
1.2%
Top 34.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
OpenVAS

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-488

Affected Products

curl
oss-project·USaka wcurl, libcurl
curlLibraryLibrary
OSS Libraries / generic-library
haxx
oss-project·SEaka haxx.se
curl
OSS Libraries

Exploitability

Official Patch Available
Workaround Available
Is your org exposed to CVE-2026-19931?Request an assessment to establish which checks are appropriate for your systems. Check my exposure

References

https://curl.se/docs/CVE-2026-19931.json
curl.se
https://curl.se/docs/CVE-2026-19931.html
curl.se
https://hackerone.com/reports/3923520
hackerone.com
News mentions
1

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