Hostname spoofing via backslashes in URL

Overview

URI.js is a javascript URL mutation library (npm package urijs).

In URI.js before version 1.19.4, the hostname can be spoofed by using a backslash (\) character followed by an at (@) character. If the hostname is used in security decisions, the decision may be incorrect. Depending on library usage and attacker intent, impacts may include allow/block list bypasses, SSRF attacks, open redirects, or other undesired behavior.

For example the URL https://expected-example.com\@observed-example.com will incorrectly return observed-example.com if using an affected version. Patched versions correctly return expected-example.com. Patched versions match the behavior of other parsers which implement the WHATWG URL specification, including web browsers and Node’s built-in URL class. Version 1.19.4 is patched against all known payload variants.

Version 1.19.3 has a partial patch but is still vulnerable to a payload variant.

Recommendation

Upgrade to version 1.19.4 or later.

References

• GitHub Advisory
• CVE
• Fix Commit
• GitHub Advisory