Impact: fast-uri versions from 2.3.1 through 4.1.0 (including the 3.x line up to 3.1.3 and the 2.x line up to 2.4.2) do not treat a literal backslash character (U+005C) as an authority delimiter. Node's native WHATWG URL parser, used by fetch, undici, and Node's http and https clients, normalizes the backslash to a forward slash for special schemes such as http, https, ws, wss, ftp, and file. As a result, the two parsers extract different hosts from the same input string. Applications that use fast-uri to enforce host-based policy such as allowlists, denylists, loopback or SSRF filtering, redirect validation, or outbound proxy routing before passing the same URL into Node's URL or fetch consumers can be steered to an unintended destination, including cloud metadata endpoints, loopback, or internal hosts. Patches: upgrade to fast-uri 4.1.1, 3.1.4, or 2.4.3. Workarounds: none.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - Impact: fast-uri versions from 2.3.1 through 4.1.0 (including the 3.x line up to 3.1.3 and the 2.x line up
    to 2.4.2) do not treat a literal backslash character (U+005C) as an authority delimiter. Node's native
    WHATWG URL parser, used by fetch, undici, and Node's http and https clients, normalizes the backslash to a
    forward slash for special schemes such as http, https, ws, wss, ftp, and file. As a result, the two
    parsers extract different hosts from the same input string. Applications that use fast-uri to enforce
    host-based policy such as allowlists, denylists, loopback or SSRF filtering, redirect validation, or
    outbound proxy routing before passing the same URL into Node's URL or fetch consumers can be steered to an
    unintended destination, including cloud metadata endpoints, loopback, or internal hosts. Patches: upgrade
    to fast-uri 4.1.1, 3.1.4, or 2.4.3. Workarounds: none. (CVE-2026-16221)

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

  - Impact: fast-uri versions from 2.3.1 through 4.1.0 (including the 3.x line up to 3.1.3 and the 2.x line up     to 2.4.2) do not treat a literal backslash character (U+005C) as an authority delimiter. Node's native     WHATWG URL parser, used by fetch, undici, and Node's http and https clients, normalizes the backslash to a     forward slash for special schemes such as http, https, ws, wss, ftp, and file. As a result, the two     parsers extract different hosts from the same input string. Applications that use fast-uri to enforce     host-based policy such as allowlists, denylists, loopback or SSRF filtering, redirect validation, or     outbound proxy routing before passing the same URL into Node's URL or fetch consumers can be steered to an     unintended destination, including cloud metadata endpoints, loopback, or internal hosts. Patches: upgrade     to fast-uri 4.1.1, 3.1.4, or 2.4.3. Workarounds: none. (CVE-2026-16221)

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

ID	Name	Product	Family	Type	Severity
465201	Echo: fast-uri: security update to 2.4.3	Tenable Cloud Security	Echo Local Security Checks	Local	high
465201	Echo: fast-uri: security update to 2.4.3	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	high
445032	SCA: security update for fast-uri (GHSA-v2hh-gcrm-f6hx)	Tenable Cloud Security	SCA Checks	Local	high
445032	SCA: security update for fast-uri (GHSA-v2hh-gcrm-f6hx)	Tenable Self-Hosted Container Security	SCA Checks	Local	high
328008	Linux Distros Unpatched Vulnerability : CVE-2026-16221	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-16221

high

Tenable Plugins

high

high

high

high

high