medium6.5

CVE-2020-26291

Hostname spoofing via backslashes in URL

Impact

### 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](https://url.spec.whatwg.org/), including web browsers and [Node's built-in URL class](https://nodejs.org/api/url.html). ### 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](https://github.com/medialize/URI.js/pull/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](https://AlesandroOrtiz.com)

Affected packages

Ecosystem	Package	Affected	Fixed in
npm	`urijs`	< 1.19.4	1.19.4

Affected products

Vendor	Product	Affected versions
Uri.Js Project	Uri.Js	before 1.19.4

Weakness classification

CWE-20