CVE-2026-6276

HIGH

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

CVSS v3.1 Score

7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Published: 5/13/2026Modified: 9/15/2026

Related Intelligence (2)

CRITICALApt

Hitachi Energy RTU500 Product

<p><a href="https://github.com/cisagov/CSAF/blob/develop/csaf_files/OT/white/2026/icsa-26-293-05.json"><strong>View CSAF</strong></a></p> <h2>Summary</h2> <p><strong>Hitachi Energy is aware of vulnerabilities that affect RTU500 product versions listed in this document. These vulnerabilities if exploited can have impact on confidentiality, integrity and availability of the product. Please refer to

CVE-2026-17539CVE-2026-28388
CISA Advisories
HIGHVulnerability

NVD HIGH: CVE-2026-6276 — Using libcurl, when a custom `Host:` header is first set for an HTTP request and...

Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

CVE-2026-6276
NIST NVD

References (5)

https://curl.se/docs/CVE-2026-6276.htmlPatchVendor Advisoryhttps://curl.se/docs/CVE-2026-6276.jsonProducthttps://hackerone.com/reports/3671818ExploitIssue Trackinghttp://www.openwall.com/lists/oss-security/2026/04/29/13Mailing ListThird Party Advisoryhttps://hackerone.com/reports/3671818ExploitIssue Tracking