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Vulnerability record · CVE-2026-6276 · published 13 May 2026

CVE-2026-6276: Haxx curl origin validation error vulnerability

Haxx · Curl

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.

7.5 CVSS 3.1 High EPSS 0.35% · top 74.0% CWE-346 · Origin validation errorCWE-319 · Cleartext transmission
7.5CVSS 3.1 base score
0.35%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
5References, 2 tagged exploit
15 Sep 2026Last modified by NVD

Description

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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://curl.se/docs/CVE-2026-6276.html PatchVendor Advisory
https://curl.se/docs/CVE-2026-6276.json Product
https://hackerone.com/reports/3671818 ExploitIssue TrackingThird Party Advisory
http://www.openwall.com/lists/oss-security/2026/04/29/13 Mailing ListThird Party Advisory
https://hackerone.com/reports/3671818 ExploitIssue TrackingThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-6276), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.