# CVE-2026-16221: node-ajv: 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)...

CVE-2026-16221 is fixed in node-ajv on 1 platform by DEBIAN-CVE-2026-16221 (version 8.20.0~ds+~cs7.1.2-1), released August 6, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-16221
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0044
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 19, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | node-ajv Debian 14 | 8.20.0~ds+~cs7.1.2-1 | [DEBIAN-CVE-2026-16221](https://patchblox.com/security/data/fix/linux/debian-cve-2026-16221.md) | Aug 6, 2026 |

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Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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