Successfully using libcurl to do a transfer over a specific HTTP proxy (`proxyA`) with **Digest** authentication and then changing the proxy host to a second one (`proxyB`) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the `Proxy-Authorization:` header field meant for `proxyA`, to `proxyB`.

An update of the curl package has been released.

The remote Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8227-1 advisory.

    It was discovered that curl incorrectly reused non-TLS connections when TLS was required in some STARTTLS     configurations. A remote attacker could possibly use this issue to obtain sensitive information.
    (CVE-2026-4873)

    It was discovered that curl incorrectly reused certain HTTP Negotiate connections. A remote attacker could     possibly use this issue to obtain sensitive information. (CVE-2026-5545)

    It was discovered that curl incorrectly reused certain SMB connections. A remote attacker could possibly     use this issue to obtain sensitive information. (CVE-2026-5773)

    It was discovered that curl could leak proxy credentials when handling redirects in some configurations. A     remote attacker could possibly use this issue to obtain sensitive information. (CVE-2026-6253)

    It was discovered that curl could leak cookies because of stale custom cookie host handling in some     requests. A remote attacker could possibly use this issue to obtain sensitive information. (CVE-2026-6276)

    It was discovered that curl could leak .netrc credentials when reusing proxy connections in some     situations. A remote attacker could possibly use this issue to obtain sensitive information.
    (CVE-2026-6429)

    It was discovered that curl could leak Digest authentication state when switching proxies in some     situations. A remote attacker could possibly use this issue to obtain sensitive information.
    (CVE-2026-7168)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

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

The version of libcurl installed on the remote host is 7.12.0 prior to 8.20.0. It is, therefore, affected by a cross-proxy digest auth state leak vulnerability:

  - libcurl improperly handles Digest authentication headers when reusing handles across different HTTP     proxies. When a client switches from one proxy to another using the same connection handle, the     library incorrectly forwards the Proxy-Authorization header intended for the first proxy to the     second one. An evil proxyB could use this incoming request header field to impersonate the client     in communicating with proxyA, as the header contains the authenticated state. (CVE-2026-7168)

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.

  - Successfully using libcurl to do a transfer over a specific HTTP proxy (`proxyA`) with **Digest**     authentication and then changing the proxy host to a second one (`proxyB`) for a second transfer, reusing     the same handle, makes libcurl wrongly pass on the `Proxy-Authorization:` header field meant for `proxyA`,     to `proxyB`. (CVE-2026-7168)

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

ID	Name	Product	Family	Severity
315300	Photon OS 4.0: Curl PHSA-2026-4.0-1020	Nessus	PhotonOS Local Security Checks	medium
312298	Ubuntu 22.04 LTS / 24.04 LTS / 25.10 / 26.04 LTS : curl vulnerabilities (USN-8227-1)	Nessus	Ubuntu Local Security Checks	high
311422	libcurl 7.12.0 < 8.20.0 Cross-Proxy Digest Auth State Leak	Nessus	Misc.	medium
310991	Linux Distros Unpatched Vulnerability : CVE-2026-7168	Nessus	Misc.	medium

Detections

Analytics

CVE-2026-7168

medium

Tenable Plugins

medium

high

medium

medium