Vulnerability Description
A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared. While the documentation states that passing NULL to `CURLOPT_REFERER` suppresses the header, the option failed to clear the internal state. As a result the previous referrer string was erroneously reused and sent in subsequent requests, potentially leaking sensitive information to unintended servers.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Haxx | Curl | >= 8.18.0, < 8.21.0 |
References
- https://curl.se/docs/CVE-2026-9546.htmlPatchVendor Advisory
- https://curl.se/docs/CVE-2026-9546.jsonThird Party Advisory
- https://hackerone.com/reports/3754343ExploitIssue TrackingThird Party Advisory
- https://hackerone.com/reports/3754343ExploitIssue TrackingThird Party Advisory
FAQ
What is CVE-2026-9546?
CVE-2026-9546 is a vulnerability with a CVSS score of 7.5 (HIGH). A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared. While the documentation states that passing NULL to `CURLOPT_REFERER` suppresses the header, the o...
How severe is CVE-2026-9546?
CVE-2026-9546 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-2026-9546?
Check the references section above for vendor advisories and patch information. Affected products include: Haxx Curl.