CVE-2025-6979 Overview
CVE-2025-6979 is an authentication bypass vulnerability affecting the Captive Portal feature documented in Arista Security Advisory #0123. The flaw allows an attacker to circumvent the authentication mechanism that the Captive Portal enforces on network clients. Successful exploitation grants network access without supplying valid credentials, compromising the confidentiality, integrity, and availability of the protected network segment. The weakness is classified as [CWE-287] Improper Authentication. Exploitation occurs over the network and requires user interaction, but no privileges are needed on the target system.
Critical Impact
An unauthenticated attacker on an adjacent network can bypass Captive Portal login enforcement and gain access to resources that should be restricted to authenticated users.
Affected Products
- Arista network products implementing the Captive Portal feature (see Arista Security Advisory #0123 for the authoritative product and version list)
Discovery Timeline
- 2025-10-23 - CVE-2025-6979 published to NVD
- 2026-04-15 - Last updated in NVD database
Technical Details for CVE-2025-6979
Vulnerability Analysis
The Captive Portal feature is designed to intercept HTTP traffic from unauthenticated clients and redirect them to a login page before granting network access. CVE-2025-6979 breaks this enforcement model, allowing a client to reach protected resources without completing the authentication workflow.
The vulnerability requires user interaction, indicating that an attacker likely needs a victim to trigger a specific request, click a crafted link, or visit a controlled page while connected to the captive network. Because the attack proceeds over the network with no privileges required, the attacker only needs reachability to the Captive Portal interface.
The weakness maps to [CWE-287] Improper Authentication, meaning the portal accepts or fails to validate session state in a condition where it should reject the request. The result is full compromise of access controls that the portal is intended to enforce.
Root Cause
The root cause is improper authentication enforcement within the Captive Portal request-handling logic. The portal either fails to validate authentication state on certain request paths or trusts client-supplied data that should not be trusted. Refer to Arista Security Advisory #0123 for vendor-confirmed technical details.
Attack Vector
An attacker with network reachability to the Captive Portal endpoint coerces a user into performing an action that triggers the vulnerable code path. Once the bypass succeeds, the attacker's client is treated as authenticated and is permitted to communicate beyond the portal's enforcement boundary. No valid credentials, tokens, or prior session are required.
No public proof-of-concept or in-the-wild exploitation has been reported. Verified exploitation details are not available outside of the vendor advisory.
Detection Methods for CVE-2025-6979
Indicators of Compromise
- Captive Portal session logs showing client devices reaching protected resources without a corresponding successful authentication event.
- Unexpected MAC or IP addresses appearing in the authenticated client table immediately after HTTP requests to the portal.
- Repeated or malformed requests to Captive Portal endpoints preceding outbound traffic from previously unauthenticated clients.
Detection Strategies
- Correlate authentication events with subsequent network flows to identify clients that gain access without a matching login transaction.
- Inspect web server and portal application logs for anomalous request sequences targeting authentication or redirect handlers.
- Baseline normal Captive Portal authentication patterns and alert on deviations, including unusual user agents or rapid state transitions.
Monitoring Recommendations
- Forward Captive Portal, RADIUS, and DHCP logs to a centralized analytics platform for cross-source correlation.
- Monitor for outbound traffic from guest or quarantine VLANs that should be gated by the portal.
- Enable verbose logging on the Captive Portal subsystem during incident triage to capture request bodies and session identifiers.
How to Mitigate CVE-2025-6979
Immediate Actions Required
- Review Arista Security Advisory #0123 to confirm whether deployed products and versions are affected.
- Apply the vendor-provided fixed software release as soon as it is available in your change-management window.
- Restrict administrative and management interfaces of devices running Captive Portal to trusted networks only.
- Audit recent Captive Portal authentication logs for evidence of bypass attempts or unauthorized access.
Patch Information
Arista has published remediation guidance and fixed versions in Security Advisory #0123. Consult the advisory for the specific fixed releases, hotfix availability, and upgrade paths applicable to each affected platform. No alternative patch source should be used.
Workarounds
- Where patching is not immediately possible, disable the Captive Portal feature on affected devices and substitute an alternative authentication mechanism such as 802.1X.
- Place Captive Portal-protected segments behind an additional enforcement layer, such as a firewall policy that requires authenticated VPN or NAC posture before permitting upstream access.
- Limit network reachability to the Captive Portal interface to known client subnets to reduce exposure to opportunistic attackers.
# Refer to vendor advisory for exact CLI syntax for affected platforms
# Example: disable captive portal where supported as a temporary workaround
# configure terminal
# no captive-portal enable
# end
# write memory
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
