GHSA-cpm7-cfpx-3hvp is a medium-severity (CVSS 4.8) Cross-site Scripting (XSS) vulnerability in gov.nsa.emissary:emissary. A fix is available for gov.nsa.emissary:emissary — see the affected versions and patch details below.
Emissary has Stored XSS via Navigation Template Link Injection
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-cpm7-cfpx-3hvp.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-cpm7-cfpx-3hvp plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 376,715 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
gov.nsa.emissary:emissaryReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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)
{{#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
navItemsconfiguration - User interaction (clicking the link) is required
- The Emissary web interface is typically accessed only by authenticated operators within a trusted network
Remediation
Fixed in PR #1293, merged into release 8.39.0.
Server-side link validation — NavAction.java
An allowlist regex was added that only permits http://, https://, or
site-relative (/) URLs:
private static final Pattern VALID_LINK = Pattern.compile("^(https?:/)?/.*");
private static boolean isValidLink(String link) {
if (!VALID_LINK.matcher(link).matches()) {
logger.warn("Skipping invalid navigation link '{}'", link);
return false;
}
return true;
}
Invalid links are logged and silently dropped from the rendered navigation.
Template hardening — nav.mustache
Added rel="noopener noreferrer" to all navigation link anchor tags as a
defense-in-depth measure:
<a class="nav-link" href="{{link}}" rel="noopener noreferrer">{{display}}</a>
Tests were added to verify that javascript: and ftp:// URIs are rejected
while http://, https://, and site-relative (/path) links are accepted.
Workarounds
If upgrading is not immediately possible, audit the navigation configuration
to ensure all navItems link values use only http://, https://, or
relative (/) URL schemes.
References
- PR #1293 — validate nav links
- Original report: GHSA-wjqm-p579-x3ww
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | gov.nsa.emissary:emissary | all versions | 8.39.0gov.nsa.emissary:emissary:8.39.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for gov.nsa.emissary:emissary, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update gov.nsa.emissary:emissary to 8.39.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cpm7-cfpx-3hvp is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-cpm7-cfpx-3hvp can be triaged on real exposure rather than presence alone.
Tailored to GHSA-cpm7-cfpx-3hvp. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-cpm7-cfpx-3hvp in your dependencies?
O3 Security finds GHSA-cpm7-cfpx-3hvp across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.