CVE-2026-102019 in Junos OS
Summary
by MITRE • 10/14/2026
An Improper Validation of Specified Quantity in Input vulnerability in the rpd process of Juniper Networks Junos OS and Junos Evolved allows an unauthenticated adjacent attacker to cause a denial-of-service condition via a malformed RIPv2 message.
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Analysis
by VulDB Data Team • 10/15/2026
The identified vulnerability represents a critical flaw within the Routing Protocol Daemon, commonly referred to as rpd, which is responsible for managing dynamic routing protocols in Juniper Networks operating systems including Junos OS and Junos Evolved. This specific weakness stems from an improper validation of specified quantities found within input data structures. The core technical issue lies in the failure of the application to adequately verify or bound numerical values associated with incoming network packets before processing them. When a malformed Routing Information Protocol version 2, known as RIPv2, message is received, the daemon does not correctly check if the declared quantity of routes or other enumerated fields exceeds expected limits or falls within valid ranges. This lack of rigorous input sanitization allows an attacker to inject crafted data that triggers unexpected behavior during parsing and memory allocation routines.
The operational impact of this vulnerability is severe, primarily manifesting as a denial-of-service condition against the affected device. Because the flaw resides in the rpd process, which is essential for maintaining routing table integrity and network connectivity, any disruption to its stability directly compromises the router's ability to forward traffic correctly. An unauthenticated attacker positioned on an adjacent network segment can exploit this weakness by sending specially crafted RIPv2 messages that contain invalid or excessively large quantity specifications. Upon processing these malformed packets, the rpd process may encounter a buffer overflow, integer overflow, or resource exhaustion scenario, leading to a crash of the daemon. In many Junos implementations, such crashes often result in a full system reboot or require manual intervention by network administrators to restore service, thereby causing significant downtime and potential loss of connectivity for all devices relying on this router as a gateway or transit point.
From a threat modeling perspective, this vulnerability aligns with CWE-20 Improper Input Validation, specifically regarding the failure to validate numerical constraints within protocol messages. It also maps closely to ATT&CK technique T1498 Network Denial of Service, where an adversary disrupts availability by exploiting resource consumption flaws in network services. The requirement for adjacency highlights that this is a layer-two or local network attack vector, meaning the attacker must have direct access to the same broadcast domain as the vulnerable router interface running RIPv2. This constraint limits the remote exploitability but increases the risk within internal enterprise networks where trusted zones may inadvertently expose routing protocols to untrusted segments if not properly segmented.
Mitigation strategies for this vulnerability involve both immediate operational controls and long-term architectural improvements. The most effective short-term mitigation is to disable the RIPv2 service on interfaces that do not strictly require it, thereby removing the attack surface entirely. If RIPv2 must remain active, administrators should implement strict access control lists or prefix filters at the interface level to restrict incoming routing updates from untrusted sources. Furthermore, deploying network intrusion detection systems capable of identifying malformed protocol packets can provide an additional layer of defense by dropping suspicious traffic before it reaches the vulnerable daemon. It is imperative for organizations running affected versions of Junos OS and Junos Evolved to apply vendor-provided software patches as soon as they become available, ensuring that the input validation logic in the rpd process is updated to correctly handle edge cases and malformed quantities without crashing.