Vulnerability Description
Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a different one (`hostB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Authorization:` header field meant for `hostA`, to `hostB`.
CVSS Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Haxx | Curl | >= 7.10.6, < 8.21.0 |
Related Weaknesses (CWE)
References
- https://curl.se/docs/CVE-2026-11856.htmlPatchVendor Advisory
- https://curl.se/docs/CVE-2026-11856.jsonVendor Advisory
- https://hackerone.com/reports/3793260ExploitIssue TrackingThird Party Advisory
- https://hackerone.com/reports/3793260ExploitIssue TrackingThird Party Advisory
FAQ
What is CVE-2026-11856?
CVE-2026-11856 is a vulnerability with a CVSS score of 9.8 (CRITICAL). Successfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a different one (`hostB`) for a second transfer, reusing ...
How severe is CVE-2026-11856?
CVE-2026-11856 has been rated CRITICAL with a CVSS base score of 9.8/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-11856?
Check the references section above for vendor advisories and patch information. Affected products include: Haxx Curl.