CVE-2026-25620 Overview
CVE-2026-25620 is a command injection vulnerability in the Captive Portal application framework of Arista Edge Threat Management - Arista Next Generation Firewall (NGFW). The flaw is classified as an encrypted password command injection issue and is tracked under CWE-78 (Improper Neutralization of Special Elements used in an OS Command). Only version 17.4.0 is affected; earlier releases are not exposed. Authenticated attackers with high privileges can inject operating system commands through the affected component over the network. Successful exploitation leads to command execution within the NGFW context, with downstream impact on confidentiality, integrity, and availability of subsequent systems.
Critical Impact
Authenticated attackers can inject arbitrary OS commands into the Captive Portal framework on Arista NGFW 17.4.0, compromising the firewall and connected network segments.
Affected Products
- Arista Edge Threat Management - Next Generation Firewall (NGFW) version 17.4.0
- Captive Portal application framework component within Arista NGFW
- Earlier NGFW software releases (prior to 17.4.0) are not exposed
Discovery Timeline
- 2026-06-05 - CVE-2026-25620 published to NVD
- 2026-06-08 - Last updated in NVD database
Technical Details for CVE-2026-25620
Vulnerability Analysis
The vulnerability resides in the Captive Portal application framework of Arista NGFW 17.4.0. Captive Portal subsystems typically intercept HTTP/HTTPS sessions to enforce authentication policies before allowing network access. In this release, the framework processes an encrypted password parameter without proper neutralization of shell metacharacters. When the value reaches an underlying OS command invocation, attacker-controlled content is interpreted by the system shell. This issue is mapped to CWE-78, OS Command Injection.
Root Cause
The root cause is improper input validation and unsafe construction of shell commands inside the Captive Portal handler. The encrypted password field is concatenated or passed into a command invocation without strict allow-list filtering, parameterization, or shell-escaping. Sole reliance on the field's expected format permits embedded shell control characters such as ;, |, &, backticks, and $() to break out of the intended argument context.
Attack Vector
The attack is network-based and requires high privileges, indicating that the attacker must already hold an authenticated administrative role on the NGFW. From this position, the attacker submits a crafted encrypted password value to the Captive Portal framework. The injected payload is executed by the operating system shell with the privileges of the NGFW service. The CVSS 4.0 vector reflects high confidentiality impact on the vulnerable system and low integrity and availability impact on subsequent systems. EPSS data indicates a low near-term exploitation probability at the time of publication.
No public proof-of-concept code is available. Refer to the Arista Security Advisory #0133 for vendor-supplied technical details.
Detection Methods for CVE-2026-25620
Indicators of Compromise
- Unexpected child processes spawned by the Captive Portal service on the NGFW appliance, particularly shells such as /bin/sh or /bin/bash invoked outside normal operational patterns.
- Captive Portal log entries containing shell metacharacters (;, |, &, `, $() within password or authentication fields.
- Outbound network connections originating from the NGFW management plane to unfamiliar hosts shortly after Captive Portal authentication attempts.
Detection Strategies
- Monitor administrative authentication events on Arista NGFW 17.4.0 for use of high-privilege accounts immediately followed by Captive Portal configuration or authentication activity.
- Inspect Captive Portal application logs for malformed or oversized encrypted password fields that deviate from expected ciphertext length and character sets.
- Correlate process execution telemetry from the appliance with HTTP/HTTPS requests directed at Captive Portal endpoints to identify command-injection chains.
Monitoring Recommendations
- Forward Arista NGFW syslog and audit data to a centralized analytics platform and alert on anomalous shell invocations tied to web service users.
- Track creation of new files, cron entries, or persistence artifacts on the NGFW following Captive Portal activity.
- Review privileged account usage on the NGFW and alert on logins from new source IP ranges or outside change windows.
How to Mitigate CVE-2026-25620
Immediate Actions Required
- Identify all Arista NGFW deployments running version 17.4.0 and apply the fixed release listed in Arista Security Advisory #0133.
- Restrict administrative access to the NGFW management interface to a small set of trusted source addresses using ACLs or out-of-band management networks.
- Rotate credentials for all NGFW administrative accounts and review recent privileged sessions for unexplained activity.
Patch Information
Arista has documented the issue and remediation in Arista Security Advisory #0133. Administrators should upgrade affected NGFW systems to the fixed version referenced in the advisory. Versions earlier than 17.4.0 are not affected and do not require this patch.
Workarounds
- Disable the Captive Portal application framework on NGFW 17.4.0 until the patch is applied, if operationally feasible.
- Limit administrative role assignment so that the high-privilege roles required for exploitation are granted only to a minimal set of audited accounts.
- Enforce multi-factor authentication on all NGFW administrative logins to reduce the likelihood of credential-based pivots into exploitation.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
