CVE-2025-2767: Arista NG Firewall RCE Vulnerability

CVE-2025-2767 Overview

CVE-2025-2767 is a critical Cross-Site Scripting (XSS) vulnerability in Arista NG Firewall that enables remote code execution. This vulnerability allows remote attackers to execute arbitrary code on affected installations of Arista NG Firewall through the exploitation of improper validation of the User-Agent HTTP header. The flaw results from the lack of proper validation of user-supplied data, which can lead to the injection of arbitrary scripts that execute in the context of root.

Critical Impact

Successful exploitation allows attackers to execute code with root privileges on affected Arista NG Firewall installations, potentially leading to complete system compromise, unauthorized network access, and lateral movement across protected infrastructure.

Affected Products

• Arista NG Firewall version 17.1.1
• Arista NG Firewall (all versions potentially affected)

Discovery Timeline

• 2025-04-23 - CVE-2025-2767 published to NVD
• 2025-08-14 - Last updated in NVD database

Technical Details for CVE-2025-2767

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation - Cross-Site Scripting). The specific flaw exists within the processing of the User-Agent HTTP header within the Arista NG Firewall management interface. When user-supplied data is passed through this header, the application fails to properly sanitize and validate the input before processing it, creating an injection point for malicious scripts.

The attack requires network access and minimal user interaction, making it exploitable across organizational boundaries. The scope is changed, meaning successful exploitation can impact resources beyond the vulnerable component's security scope. Complete confidentiality, integrity, and availability impacts are possible, as the injected code executes with root-level privileges on the firewall system.

This vulnerability was tracked by the Zero Day Initiative as ZDI-CAN-24407 and disclosed as ZDI-25-181.

Root Cause

The root cause of this vulnerability lies in the insufficient input validation and output encoding of the User-Agent HTTP header field. When the firewall processes HTTP requests, the User-Agent header value is incorporated into internal operations without adequate sanitization. This allows specially crafted header values containing malicious script content to be processed and executed by the system. The lack of proper contextual output encoding transforms what should be a benign header field into a vector for script injection that achieves code execution with elevated privileges.

Attack Vector

The attack vector for CVE-2025-2767 is network-based, requiring an attacker to craft malicious HTTP requests with specially constructed User-Agent headers targeting the Arista NG Firewall. The exploitation chain involves:

1. An attacker sends HTTP requests to the target firewall with a maliciously crafted User-Agent header containing embedded script code
2. The firewall's web interface processes the User-Agent header without proper validation or encoding
3. The injected script content is executed within the context of an authenticated user's session
4. Due to the privileged nature of the firewall management interface, the executed code runs with root privileges

While minimal user interaction is required, the network accessibility of this attack combined with root-level code execution makes this vulnerability particularly dangerous for exposed firewall management interfaces.

Detection Methods for CVE-2025-2767

Indicators of Compromise

• HTTP requests to the Arista NG Firewall management interface containing suspicious User-Agent headers with JavaScript or encoded script content
• Unusual User-Agent strings containing <script>, HTML entities, or encoded payloads targeting the firewall interface
• Unexpected processes or commands executed with root privileges on the firewall system
• Anomalous network traffic originating from the firewall to external command-and-control infrastructure

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests with malicious User-Agent header patterns
• Deploy network intrusion detection signatures to identify XSS payload patterns in HTTP headers targeting Arista NG Firewall
• Enable comprehensive logging on the firewall management interface and monitor for anomalous User-Agent values
• Utilize endpoint detection and response (EDR) solutions to monitor for unexpected process execution on firewall hosts

Monitoring Recommendations

• Configure alerting for User-Agent headers exceeding typical length thresholds or containing script-related syntax
• Monitor for new or modified files within the firewall's web application directories
• Track authentication attempts and session activity on the firewall management interface
• Establish baseline behavior for firewall processes and alert on deviations indicating potential compromise

How to Mitigate CVE-2025-2767

Immediate Actions Required

• Restrict access to the Arista NG Firewall management interface to trusted internal networks or VPN connections only
• Implement network segmentation to limit exposure of firewall management interfaces
• Apply vendor patches immediately upon availability from Arista
• Review firewall logs for any signs of exploitation attempts or successful compromise

Patch Information

Organizations should consult Arista's official security advisories and patch documentation for remediation guidance. The vulnerability details are available through the Zero Day Initiative Advisory ZDI-25-181. Contact Arista support for information on patched firmware versions and update procedures for affected NG Firewall deployments.

Workarounds

• Implement strict access control lists (ACLs) to limit management interface access to authorized administrator IP addresses only
• Deploy a reverse proxy or WAF in front of the management interface with strict header validation rules
• Disable remote management access entirely if not operationally required, using only local console access
• Enable additional authentication mechanisms such as client certificates for management interface access

# Example: Restrict firewall management access via iptables (apply on management network)
# Limit access to specific administrator subnet
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Log suspicious connection attempts
iptables -A INPUT -p tcp --dport 443 -j LOG --log-prefix "NG-FW-MGMT-BLOCKED: "