VulnerabilityPublished 7 Apr 2026Updated 4 Nov 2026

CVE-2026-35571: Gov.nsa.emissary:emissary: Emissary has Stored XSS via Navigation Template Link Injection

Affects gov.nsa.emissary:emissarySource GCVE Database

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Authoritative record:CVE-2026-35571· Medium 4.8

Not known to be exploited · CVSS 4.8 Medium : upgrade to 8.39.0 when convenient.

Data as of 4 Nov 2026, 23:29 UTC

CVSS 3.1 base score

4.8Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 8.39.0

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: High
User Interaction: Required
Scope: Changed
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: High: The attacker is authorized with (i.e., requires) privileges that provide significant (e.g., administrative) control over the vulnerable component that could affect component-wide settings and files.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Apr 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 4 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade gov.nsa.emissary:emissary to 8.39.0.

Affected software

Product	Affected	Fixed in
Mavengov.nsa.emissary:emissary	Affected <8.39.0	Fixed in 8.39.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade Emissary to version 8.39.0 or later, which includes server-side validation of navigation links to allow only http://, https://, or relative URLs, and template hardening with rel="noopener noreferrer" attributes. If immediate upgrade is not possible, audit the navigation configuration to ensure all navItems links use only allowed URL schemes (http://, https://, or relative paths).

Description

Emissary versions prior to 8.39.0 contain a stored cross-site scripting (XSS) vulnerability in the navigation template. The vulnerability arises because navigation link URLs are interpolated into href attributes without validating the URL scheme, allowing an administrator to inject javascript: URIs. Authenticated users who click such malicious links can execute arbitrary scripts in their browser context, potentially leading to session hijacking and actions performed on their behalf. Exploitation requires administrative access to modify navigation configuration and user interaction. The issue is fixed in version 8.39.0 by adding server-side URL scheme validation and template hardening.

Impact

Successful exploitation allows an attacker with administrative access to inject malicious javascript: links into the navigation menu, leading to stored XSS. This can result in session hijacking via cookie theft and unauthorized actions performed on behalf of authenticated users who click the malicious link. However, exploitation requires both administrative privileges to modify navigation configuration and user interaction (clicking the link). The Emissary interface is typically accessed by trusted authenticated operators, which may limit exposure.

Summary

The Emissary web interface uses Mustache templates to render navigation links from configuration-controlled values without validating URL schemes. Specifically, the {{link}} value is inserted into href attributes without checking for dangerous schemes like javascript:. This allows an administrator with configuration access to inject javascript: URIs, resulting in stored XSS that executes when authenticated users click the malicious navigation link. The vulnerability requires administrative privileges to modify the navItems configuration and user interaction to trigger. The fix, merged in release 8.39.0, adds server-side validation restricting links to http://, https://, or relative URLs, and adds rel="noopener noreferrer" to anchor tags as a defense-in-depth measure. Tests ensure that javascript: and ftp:// links are rejected while valid schemes are accepted.

CWE-79Improper Neutralization of Input During Web Page Generation (Cross-site Scripting) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2026, 23:27 UTC

WeaknessesCWE-79

Technical details

References

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