CVE-2026-9546
High
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.
SeverityHigh
CVSS7.5
Exploit probability—
ProductHaxx Curl
PublishedJul 3, 2026
First seenJul 3, 2026
Weakness typeCWE-200Sensitive information exposure
How to fix
Update
- haxx curl8.21.0 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| haxx curl | 8.18.0 ≤ v < 8.21.0 | 8.21.0 |
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