Vulnerability 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 Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Haxx | Curl | >= 7.71.0, < 8.20.0 |
Related Weaknesses (CWE)
References
- https://curl.se/docs/CVE-2026-6276.htmlPatchVendor Advisory
- https://curl.se/docs/CVE-2026-6276.jsonProduct
- https://hackerone.com/reports/3671818ExploitIssue TrackingThird Party Advisory
- http://www.openwall.com/lists/oss-security/2026/04/29/13Mailing ListThird Party Advisory
- https://hackerone.com/reports/3671818ExploitIssue TrackingThird Party Advisory
FAQ
What is CVE-2026-6276?
CVE-2026-6276 is a vulnerability with a CVSS score of 7.5 (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 secon...
How severe is CVE-2026-6276?
CVE-2026-6276 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-6276?
Check the references section above for vendor advisories and patch information. Affected products include: Haxx Curl.