CVE-2018-5254 in EOS
Summary
by MITRE
Arista EOS before 4.20.2F allows remote BGP peers to cause a denial of service (Rib agent restart) via a malformed path attribute in an UPDATE message.
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Analysis
by VulDB Data Team • 01/25/2020
The vulnerability identified as CVE-2018-5254 affects Arista EOS software versions prior to 4.20.2F and represents a significant denial of service weakness within the Border Gateway Protocol implementation. This issue specifically targets the route information base agent responsible for processing BGP update messages, creating a scenario where remote malicious actors can trigger system instability through carefully crafted malformed path attributes. The vulnerability operates at the network protocol level, exploiting the parsing logic of BGP messages that are fundamental to internet routing operations.
The technical flaw manifests when the BGP rib agent encounters a malformed path attribute within an UPDATE message sent by a remote peer. This malformed data causes the agent to restart unexpectedly, leading to temporary disruption of routing services and potential network instability. The vulnerability stems from inadequate input validation and error handling within the BGP message processing pipeline, where the system fails to properly sanitize or reject malformed attributes before attempting to process them. This weakness aligns with CWE-129, which addresses improper validation of input boundaries, and specifically demonstrates how insufficient validation can lead to service disruption in network infrastructure components.
The operational impact of this vulnerability extends beyond simple service interruption as it affects the core routing functionality of Arista network devices. When the rib agent restarts, it temporarily removes the device from the routing decision process, potentially causing routing loops, packet loss, or temporary network partitions. Network administrators may experience unexpected service degradation or complete routing failures depending on the network topology and the number of affected devices. The remote nature of the attack means that adversaries can exploit this weakness from outside the network perimeter without requiring physical access or authentication credentials, making it particularly dangerous in production environments where BGP peers may be exposed to untrusted networks.
Mitigation strategies for CVE-2018-5254 primarily involve upgrading affected Arista EOS devices to version 4.20.2F or later, which includes patched BGP message validation routines. Network administrators should also implement BGP monitoring and alerting systems to detect unusual rib agent restart patterns that may indicate exploitation attempts. Additional protective measures include implementing BGP session filtering, rate limiting BGP updates from untrusted peers, and configuring proper access controls to limit which external peers can establish BGP sessions with critical network infrastructure. From an ATT&CK framework perspective, this vulnerability maps to T1071.004 for application layer protocol and T1499.004 for network disruption, representing both protocol-level exploitation and service availability attacks that could be leveraged as part of broader network compromise operations.