GHSA-hh8m-fm6v-7cvg

Angular: Sanitization bypass via directive host bindings on concrete host elements in @angular/core and @angular/compiler

Angular automatically sanitizes untrusted values bound to security-sensitive DOM sinks (such as `href`, `src`, `action`, `xlink:href`, and `data`) to protect against Cross-Site Scripting (XSS). Prior to the fix, the Angular compiler determined the `SecurityContext` for directive host bindings (`host: {'[attr.href]': 'value'}` or `@HostBinding('attr.href')`) based solely on the declaring directive or component selector at compile time, rather than the concrete host element that the directive was applied to. When a directive with a security-sensitive host binding was applied to a different concrete host element—such as through: - `hostDirectives` composition, - Class inheritance of host bindings, - Dynamic component instantiation (`createComponent` with custom `hostElement` or dynamic directives), - Elements with SVG/MathML namespaces (e.g. `<svg:a>`, `<math>`), or - Elements using tag-neutral selectors (e.g. `:not(...)`), the compiler either failed to associate a sanitizer with the host binding or attached an incorrect security context. As a result, untrusted inputs (e.g. `javascript:...` URLs) bound via the host binding would be written to the DOM attribute without passing through Angular's built-in sanitizer. ### Impact An attacker capable of controlling the value bound to an affected directive host binding could execute arbitrary JavaScript in the user's browser context (Cross-Site Scripting). ### Patches This issue has been resolved in versions: - `22.1.0` - `21.2.20` - `20.3.28` ### Workarounds Ensure that any user-controlled values assigned to properties bound via directive host bindings are explicitly sanitized using `DomSanitizer.sanitize(SecurityContext.URL, ...)` before assignment, or restrict the input to validated safe URL schemes (e.g. `http://`, `https://`).