CVE-2026-19931
Negotiate ambient user conn reuse
Published Sep 6, 2026
CVSS 3.1 · 9.8 Critical
EPSS < 1%
KEV · Not listed
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.
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.
Affected Products
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CVE record
-
NVD configurations
-
Red Hat packages
No data
-
OpenCVE enrichment
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| curl | curl | unaffected |
|
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| curl | curl | unaffected |
|
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| curl | curl | unaffected |
|
No data.
| Vendor | Product | Versions | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Curl | Curl |
|
Remediation
Tracking
Advisories
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.
Exploit prediction score: < 1% (0.747% probability within 30 days)
Exploitation poc
Automatable yes
Technical Impact total
References
History
Sep 16, 2026 12:15 AM
Weaknesses updated. Added references. Scoring metrics updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-613 | |
| References |
| |
| Metrics |
threat_severity
|
threat_severity
|
Sep 11, 2026 11:45 PM
First appearance in the feed. Affected versions updated. Affected vendors updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Haxx
Haxx curl |
|
| CPEs | cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Haxx
Haxx curl |
Sep 8, 2026 7:00 PM
Weaknesses updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-269 CWE-668 |
Sep 8, 2026 4:30 PM
Weaknesses updated. Scoring metrics updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| Weaknesses | CWE-488 | |
| Metrics |
cvssV3_1
|
Sep 6, 2026 7:45 PM
First appearance in the feed. Weaknesses updated. Affected vendors updated
View changes
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Curl
Curl curl |
|
| Weaknesses | CWE-269 CWE-668 |
|
| Vendors & Products |
Curl
Curl curl |
Sep 6, 2026 6:00 PM
Description updated. Title updated. Added references
View changes
| 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 |
|