CVE-2026-25624: Arista NG Firewall XSS Vulnerability

CVE-2026-25624 Overview

CVE-2026-25624 is a stored cross-site scripting (XSS) vulnerability in the web user interface dashboard layout of Arista Edge Threat Management — Arista Next Generation Firewall (NGFW). The flaw stems from unvalidated user-supplied variables that are echoed back to administrative profiles, allowing attacker-controlled payloads to execute in the browser context of authenticated administrators. The issue is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation).

Critical Impact
An authenticated attacker with high privileges can inject script payloads that execute in another administrator's session, enabling session abuse, configuration tampering, and pivoting within the NGFW management plane.

Affected Products

Arista Edge Threat Management — Next Generation Firewall (NGFW)
arista:ng_firewall (all versions prior to the fix referenced in Arista Security Advisory #0133)
Web user interface dashboard layout component

Discovery Timeline

2026-06-05 - CVE-2026-25624 published to NVD
2026-06-08 - Last updated in NVD database

Technical Details for CVE-2026-25624

Vulnerability Analysis

The vulnerability resides in the dashboard layout rendering logic of the Arista NGFW web administrative interface. User-supplied input persisted into dashboard layout configuration is reflected back into administrative profile pages without proper output encoding or input sanitization. When an administrator loads the affected dashboard view, the embedded payload renders inside the trusted origin of the management interface.

Because the payload executes within an authenticated administrator's browser session, it inherits full session privileges. An attacker can leverage this to issue authenticated API calls, modify firewall rules, exfiltrate configuration data, or stage further attacks against the management network.

Exploitation requires an authenticated attacker with administrative-level access to inject the payload, and a separate administrator must view the affected dashboard for the script to execute. This user-interaction requirement and high-privilege precondition constrain the practical attack surface but do not eliminate risk in multi-administrator environments.

Root Cause

The root cause is missing contextual output encoding when the dashboard layout serializes user-controlled fields into HTML responses. The application trusts values stored by privileged users and renders them as markup rather than escaping them as text, violating the principle of treating all stored input as untrusted at render time.

Attack Vector

The attack is delivered over the network via the NGFW administrative web interface. An authenticated administrator submits a crafted value into a dashboard layout field. The payload persists server-side and is later echoed to any administrator who loads the dashboard, where it executes JavaScript inside the management session context.

No verified proof-of-concept code is publicly available for CVE-2026-25624. Consult the Arista Security Advisory #0133 for vendor-supplied technical details.

Detection Methods for CVE-2026-25624

Indicators of Compromise

Unexpected <script>, onerror, onload, or javascript: strings stored in NGFW dashboard layout configuration fields.
Administrative session activity originating from unusual IP addresses or user agents shortly after a dashboard load.
Unauthorized changes to firewall policy, user accounts, or appliance configuration without a corresponding administrator action.
Outbound HTTP requests from administrator browsers to attacker-controlled domains following access to the NGFW UI.

Detection Strategies

Review NGFW configuration backups and dashboard layout settings for HTML or JavaScript fragments in fields that should contain plain text.
Enable and monitor web server access logs on the NGFW for POST requests to dashboard layout endpoints from non-standard administrator accounts.
Correlate administrator login events with subsequent configuration changes to identify session abuse patterns.

Monitoring Recommendations

Forward NGFW audit logs and authentication events to a centralized SIEM for correlation and alerting on anomalous admin behavior.
Alert on creation or modification of administrator accounts, API tokens, or firewall rules outside change-management windows.
Monitor for browser-side Content Security Policy violation reports if CSP is enforced on the management interface.

How to Mitigate CVE-2026-25624

Immediate Actions Required

Apply the fixed version of Arista NG Firewall identified in Arista Security Advisory #0133.
Restrict access to the NGFW administrative web interface to a dedicated management VLAN or jump host.
Audit existing dashboard layout configurations and remove any unexpected HTML or script content.
Rotate administrator credentials and API tokens if suspicious dashboard content or session activity is identified.

Patch Information

Arista has published remediation guidance in Security Advisory #0133. Administrators should consult the advisory for the specific fixed release of arista:ng_firewall and follow the vendor's documented upgrade procedure. Validate the upgrade in a maintenance window and confirm that the dashboard layout fields are properly sanitized after patching.

Workarounds

Limit administrative access to a minimal set of trusted accounts and enforce multi-factor authentication on the management interface.
Use separate, hardened browsers or browser profiles exclusively for NGFW administration to reduce cross-context risk.
Place the NGFW management interface behind a reverse proxy that enforces a strict Content Security Policy and blocks inline script execution where feasible.
Review and remove unused or shared administrator accounts to reduce the number of users capable of injecting persistent content.

bash

# Example: restrict NGFW management access to a dedicated jump host
# (adapt to your network controls; not a substitute for the vendor patch)
iptables -A INPUT -p tcp --dport 443 -s 10.10.50.10/32 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP