Impact
If using affected versions to determine a URL's hostname, 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.
Example URL: https://expected-example.com\@observed-example.com
Escaped string: https://expected-example.com\\@observed-example.com (JavaScript strings must escape backslash)
Affected versions incorrectly return observed-example.com. 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.
Patches
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.
References
https://github.com/medialize/URI.js/releases/tag/v1.19.4 (complete fix for this bypass)
https://github.com/medialize/URI.js/releases/tag/v1.19.3 (partial fix for this bypass)
PR #233 (initial fix for backslash handling)
For more information
If you have any questions or comments about this advisory, open an issue in https://github.com/medialize/URI.js
Reporter credit
Alesandro Ortiz
References
alesandroortiz Analyst
Impact
If using affected versions to determine a URL's hostname, 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.
Example URL:
https://expected-example.com\@observed-example.comEscaped string:
https://expected-example.com\\@observed-example.com(JavaScript strings must escape backslash)Affected versions incorrectly return
observed-example.com. Patched versions correctly returnexpected-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.Patches
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.
References
https://github.com/medialize/URI.js/releases/tag/v1.19.4 (complete fix for this bypass)
https://github.com/medialize/URI.js/releases/tag/v1.19.3 (partial fix for this bypass)
PR #233 (initial fix for backslash handling)
For more information
If you have any questions or comments about this advisory, open an issue in https://github.com/medialize/URI.js
Reporter credit
Alesandro Ortiz
References