CVE-2026-101992 in Junos OS
Summary
by MITRE • 10/14/2026
An Improper Input Validation vulnerability in the routing protocol daemon (rpd) process of Juniper Networks Junos OS and Junos OS Evolved allows a configured BGP peer to cause an rpd crash via a BGP VPLS signaling update.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability resides within the Routing Protocol Daemon, commonly referred to as rpd, which is a core component of the Juniper Networks Junos Operating System and Junos OS Evolved platforms. This daemon is responsible for managing dynamic routing protocols, including Border Gateway Protocol (BGP), which facilitates the exchange of routing information between autonomous systems on the internet or within large enterprise networks. The specific flaw involves improper input validation when processing BGP Virtual Private LAN Service signaling updates. VPLS is a technology that extends Ethernet services across an IP/MPLS network by emulating a local area network over a packet-switched network, and its operation relies heavily on accurate parsing of control plane messages to establish pseudowires and manage label distribution.
The technical root cause of this vulnerability lies in the insufficient validation of specific fields within BGP VPLS signaling update packets received from configured peers. When an attacker or a misconfigured peer sends a specially crafted BGP UPDATE message containing malformed or unexpected data structures related to VPLS, the rpd process fails to properly check the integrity and bounds of this input before processing it. This lack of rigorous validation leads to memory corruption, such as buffer overflows or use-after-free conditions, which ultimately causes the routing protocol daemon to crash unexpectedly. Because BGP is a stateful protocol that maintains persistent connections with peers, an attacker who has established a legitimate BGP session can exploit this flaw repeatedly without needing authentication bypasses beyond what is already granted by the peer configuration.
The operational impact of this vulnerability is significant for network stability and availability. A successful exploitation results in the termination of the rpd process on the affected device. In most Junos OS architectures, the master Routing Engine will automatically attempt to restart the daemon, but during the downtime required for recovery, routing updates are halted, and existing BGP sessions may be torn down or suspended. This can lead to temporary loss of connectivity, route flapping, or in severe cases where multiple daemons fail or cannot recover, a complete outage of network services dependent on dynamic routing. For critical infrastructure providers or enterprises relying on high-availability designs, such crashes can trigger unnecessary failovers and degrade overall service quality.
From a classification perspective, this vulnerability is categorized under CWE-20 Improper Input Validation in the Common Weakness Enumeration database. It aligns with MITRE ATT&CK techniques related to Disruption via Denial of Service, specifically targeting network infrastructure components rather than end-user applications. The attack vector requires an authenticated BGP peer relationship, meaning it falls under a privileged scope where the attacker must already have access to configure or interact with the routing protocol on the target device. This distinguishes it from remote unauthenticated attacks but highlights risks in environments where trusted peers are compromised or misconfigured.
Mitigation strategies primarily involve applying vendor-provided software updates that patch the input validation logic within the rpd process. Administrators should ensure their Junos OS and Junos OS Evolved installations are updated to versions containing fixes for this specific issue. In scenarios where immediate patching is not feasible, network segmentation can be employed to restrict BGP peering relationships only to trusted sources with strict access control lists. Additionally, implementing BGP route filtering and monitoring tools that detect anomalous update patterns or malformed packets before they reach the routing engine can provide an additional layer of defense against exploitation attempts. Regular auditing of peer configurations and adherence to least privilege principles for network device access further reduce the attack surface associated with this vulnerability.