Emissary has Stored XSS via Navigation Template Link Injection
Date: 2026-04
Affected: maven/gov.nsa.emissary:emissary
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2026-35571
CWE: CWE-79
CVSS: 4.8 (CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N)

## Summary Mustache navigation templates interpolated configuration-controlled link values directly into `href` attributes without URL scheme validation. An administrator who could modify the `navItems` configuration could inject `javascript:` URIs, enabling stored cross-site scripting (XSS) against other authenticated users viewing the Emissary web interface. ## Details ### Vulnerable code — `nav.mustache` (line 10) ```html {{#navItems}} <li class="nav-item"> <a class="nav-link" href="{{link}}">{{display}}</a> </li> {{/navItems}} ``` The `{{link}}` value was rendered without any scheme validation. Mustache's default HTML escaping protects against injection of new HTML tags but does **not** prevent `javascript:` URIs in `href` attributes, since `javascript:` contains no characters that HTML-escaping would alter. ### Attack vector An administrator sets a navigation item's link to: ``` javascript:alert(document.cookie) ``` Any authenticated user who clicks the navigation link executes the script in their browser context. ### Impact - Session hijacking via cookie theft - Actions performed on behalf of the victim user - Requires administrative access to modify navigation configuration - Requires user interaction (clicking the malicious link) ### Mitigating factors - Exploitation requires administrative access to modify the `navItems` configuration - User interaction (clicking the link) is required - The Emissary web interface is typically accessed only by authenti


Mitigations:

Architectural layers (MAESTRO):