CVE-2026-102000 in Junos OS
Summary
by MITRE • 10/14/2026
A Reachable Assertion vulnerability in the rpd process of Juniper Networks Junos OS and Junos EVO allows an adjacent unauthenticated attacker to cause a denial of service via LDP control traffic.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability resides within the Label Distribution Protocol (LDP) implementation of the Routing Process Daemon, or rpd, in Juniper Networks Junos Operating System and Junos Evolved platforms. This component is responsible for managing label switching paths essential for Multiprotocol Label Switching networks. The specific flaw is classified as a reachable assertion failure, which indicates that under certain conditions involving malformed LDP control traffic, the software encounters an internal state inconsistency or logic error that triggers a defensive code path designed to halt execution when assumptions about data integrity are violated. Unlike memory corruption vulnerabilities such as buffer overflows that might allow for arbitrary code execution, this particular issue primarily impacts system stability and availability rather than confidentiality or integrity directly through exploitation of memory structures.
An adjacent unauthenticated attacker can exploit this vulnerability by sending specifically crafted LDP packets to the affected device. Because LDP operates at the network layer and relies on TCP connections typically established between neighboring routers, an adversary positioned within the same broadcast domain or with direct IP connectivity to the target router's management or data plane interfaces can initiate this attack without requiring valid authentication credentials for the routing protocol session in some configuration scenarios, or by exploiting weaknesses in initial handshake validation. The attacker constructs LDP messages that violate expected format constraints or state machine rules defined in RFC 5036 and related standards. When the rpd process parses these malformed packets, it fails to handle the edge case gracefully, leading to an assertion failure.
The operational impact of this vulnerability is a denial of service condition affecting the routing engine on the targeted device. Upon triggering the reachable assertion, the rpd process typically crashes or restarts automatically depending on the specific version and configuration of Junos OS. This crash results in the loss of LDP sessions with all neighboring routers that rely on this instance for label distribution. Consequently, traffic engineering paths established via MPLS are disrupted, leading to potential packet loss, routing instability, and a degradation of network performance across the affected segment. In severe cases where high availability features like Graceful Restart or Non-Stop Routing are not properly configured or fail during the restart process, the impact can extend beyond local label distribution issues to broader connectivity failures within the autonomous system.
From a classification perspective, this vulnerability aligns with CWE-617, which describes Reachable Assertion, indicating that an assertion condition is reachable via external input and leads to abnormal termination of the program. In terms of offensive security frameworks such as MITRE ATT&CK, this behavior corresponds to techniques involving resource exhaustion or service disruption, often categorized under Denial of Service impacts where the attacker aims to make a specific machine, resource, or network unavailable to its intended users by consuming excessive resources or causing crashes through malformed inputs. The attack vector is classified as adjacent because it requires physical or logical proximity to the target device on the same network segment, limiting remote exploitation over wide area networks unless other vulnerabilities are chained in conjunction with this one.
Mitigation strategies for this vulnerability primarily involve applying vendor-supplied software updates that patch the specific logic error within the LDP parser of the rpd process. Organizations should prioritize upgrading Junos OS and Junos Evolved to versions where this assertion failure has been resolved by engineering teams who have added proper validation checks before processing incoming control plane messages. In environments where immediate patching is not feasible, network segmentation can be employed to restrict access to LDP ports from untrusted or adjacent networks that do not require routing protocol adjacency with the vulnerable device. Additionally, implementing strict ingress filtering and monitoring for anomalous LDP traffic patterns using intrusion detection systems tuned for control plane anomalies can help detect attempted exploitation activities before they trigger the denial of service condition. Regular review of access control lists applied to router interfaces ensures that only authorized peers are permitted to establish TCP connections on port 646, which is standard for LDP communication.