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.

An update of the curl package has been released.

The version of libcurl installed on the remote host is 8.18.0 prior to 8.21.0. It is, therefore, affected by an information disclosure vulnerability:

  - A vulnerability in libcurl caused the HTTP Referer header to persist even when explicitly cleared,     potentially leaking sensitive information to unintended servers. (CVE-2026-9546)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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.
    (CVE-2026-9546)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
334708	Photon OS 5.0: Curl PHSA-2026-5.0-90-0951	Nessus	PhotonOS Local Security Checks	Local	critical
333502	Photon OS 4.0: Curl PHSA-2026-4.0-1061	Nessus	PhotonOS Local Security Checks	Local	critical
323000	libcurl 8.18.0 < 8.21.0 Persistent Referer Header Information Disclosure	Nessus	Misc.	Local	high
322460	Linux Distros Unpatched Vulnerability : CVE-2026-9546	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-9546

high

Tenable Plugins

critical

critical

high

high