curl: A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared
CVE-2026-9546 is fixed in curl on 1 platform, first by DEBIAN-CVE-2026-9546, released July 24, 2026. It is not reported as exploited. Patch Radar priority: 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 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.
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| curl · Debian 14 | 8.21.0~rc2-1 | DEBIAN-CVE-2026-9546 | Jul 24, 2026 |
| curl · sles 15.6 | 8.22.0-150600.4.58.1 | SUSE-SU-2026:5069-1 | Nov 7, 2026 |
| curl · sles 15.7 | 8.22.0-150700.7.33.1 | SUSE-SU-2026:5068-1 | Nov 7, 2026 |
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