CVE-2025-2826 is a vulnerability identified in Arista Networks EOS version 4.33.2F, related to improper validation of specified quantities in input, classified under CWE-1284. The issue affects the enforcement of Access Control List (ACL) policies on affected platforms, specifically impacting IPv4 ingress ACL, MAC ingress ACL, and IPv6 standard ingress ACL configurations on Ethernet or Link Aggregation Group (LAG) interfaces. Due to this vulnerability, ACL policies may not be correctly enforced for ingress packets, leading to two primary symptoms: packets that should be permitted may be erroneously dropped, and packets that should be denied may be incorrectly allowed. This misbehavior can cause network traffic to be improperly filtered, potentially disrupting legitimate communications or allowing unauthorized traffic through the network perimeter. The vulnerability has a CVSS v3.1 base score of 2.6, indicating a low severity level. The vector indicates that the attack requires adjacent network access (AV:A), high attack complexity (AC:H), low privileges (PR:L), no user interaction (UI:N), and impacts only integrity (I:L) without affecting confidentiality or availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The root cause is improper validation of input quantities related to ACL enforcement logic, which compromises the integrity of ingress packet filtering. This vulnerability could lead to inconsistent network security posture and potential exposure to unauthorized traffic or denial of legitimate traffic, depending on the ACL misapplication.

For European organizations, the impact of CVE-2025-2826 could be significant in environments relying on Arista EOS 4.33.2F for critical network infrastructure, especially where strict ingress ACL enforcement is essential for regulatory compliance and security segmentation. Misapplied ACLs may allow unauthorized traffic to bypass security controls, increasing the risk of lateral movement by attackers or data exfiltration attempts. Conversely, legitimate traffic being dropped could disrupt business operations, affecting availability of services and causing operational downtime. Sectors such as finance, telecommunications, government, and critical infrastructure operators in Europe, which often deploy Arista switches for high-performance networking, may face increased risk of network security policy violations and operational disruptions. Although the CVSS score is low, the subtle nature of the ACL enforcement failure could lead to unnoticed security gaps, making detection and response more challenging. The lack of known exploits reduces immediate risk, but organizations should remain vigilant given the potential for future exploitation once the vulnerability becomes widely known.

European organizations should take the following specific steps to mitigate this vulnerability: 1) Immediately inventory all network devices running Arista EOS 4.33.2F to identify affected systems. 2) Monitor Arista’s official channels for patches or firmware updates addressing CVE-2025-2826 and apply them promptly once available. 3) As a temporary workaround, review and tighten ingress ACL configurations to minimize reliance on potentially affected ACL types or interfaces, and consider implementing additional network segmentation to limit exposure. 4) Increase monitoring of network traffic for anomalies that could indicate ACL misbehavior, such as unexpected allowed or dropped packets, using network intrusion detection systems and log analysis. 5) Conduct targeted penetration testing and ACL validation exercises to verify the effectiveness of ingress filtering post-mitigation. 6) Engage with Arista support for guidance on interim fixes or configuration best practices to reduce risk. 7) Ensure that network change management and incident response teams are aware of this vulnerability to quickly address any suspicious network behavior. These steps go beyond generic advice by focusing on device-specific inventory, configuration review, and proactive monitoring tailored to the nature of the ACL enforcement failure.