CVE-2026-102064 in Junos OS
Summary
by MITRE • 10/15/2026
A Reachable Assertion vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an attacker to cause rpd crash via malformed BGP MCAST-VPN updates from a configured eBGP peer.
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Analysis
by VulDB Data Team • 10/15/2026
The identified vulnerability represents a critical security flaw within the Routing Protocol Daemon, known as rpd, which serves as the core component for managing dynamic routing protocols in Juniper Networks Junos OS and Junos OS Evolved environments. This specific issue is classified as a reachable assertion failure, indicating that under certain conditions involving malformed input data, the software encounters an internal state inconsistency that triggers a defensive code path designed to halt execution rather than handle the error gracefully. The attack vector specifically targets Border Gateway Protocol (BGP) operations, requiring the attacker to be in possession of a configured external BGP peer relationship with the vulnerable device. This prerequisite implies that the vulnerability is not remotely exploitable by an unauthenticated outsider on the public internet but requires either physical access or prior compromise of a network segment where eBPeering sessions are established between trusted and potentially malicious peers.
The technical mechanism behind this crash involves the processing of BGP Multicast VPN (MCAST-VPN) updates, which are used to distribute multicast routing information across virtual private networks over an MPLS backbone. When rpd receives these update messages from a configured eBGP peer, it performs validation checks on the received data structures. In this instance, specific malformed attributes or fields within the MCAST-VPN update packet violate internal assumptions made by the daemon during parsing and state machine transitions. Instead of rejecting the invalid message with an appropriate error notification to the sender, the software hits a precondition check that fails, leading directly to an assertion failure. This results in an immediate termination of the rpd process, causing a denial of service condition for all routing protocols managed by this daemon on the device.
The operational impact of this vulnerability is severe due to its potential to disrupt network stability and availability. Since rpd manages not only BGP but often other critical dynamic routing protocols such as OSPF, IS-IS, or RIP depending on configuration, a crash in this process can lead to a temporary loss of route computation and forwarding table updates across the entire device. This disruption may cause traffic blackholing, increased latency due to reconvergence delays, or even a complete outage if redundant control plane processes are not adequately isolated or if the daemon fails to restart automatically within acceptable timeframes for high-availability deployments. For organizations relying on Junos OS for critical infrastructure routing, this represents a significant risk to business continuity and network resilience.
From a classification perspective, this vulnerability aligns with CWE-617, which describes Reachable Assertion, as it involves triggering an assertion failure through external input that should have been validated earlier in the processing pipeline. Furthermore, from a tactical standpoint within the MITRE ATT&CK framework, this exploit falls under T1498 Network Denial of Service, specifically reflecting techniques aimed at exhausting resources or causing service disruption by exploiting software bugs rather than overwhelming bandwidth. The requirement for an eBGP peer configuration places it in the context of lateral movement or insider threats where an attacker has established a legitimate routing session but abuses protocol semantics to destabilize the target system.
Mitigation strategies primarily involve applying vendor-provided patches that address the input validation logic within rpd to ensure malformed MCAST-VPN updates are handled gracefully without triggering assertion failures. Until such patches are applied, network administrators should consider restricting BGP peering sessions with untrusted or external peers using strict prefix filtering and route-map policies to limit the types of updates accepted from those neighbors. Additionally, implementing control plane policing can help mitigate broader denial-of-service impacts by rate-limiting routing protocol traffic, although this may not prevent a single malformed packet from triggering an assertion failure if the validation occurs after initial acceptance into the processing queue. Regular monitoring for unexpected rpd restarts or syslog entries indicating assertion failures is also recommended to detect potential exploitation attempts in real-time.