CVE-2026-102051 in Junos OS
Summary
by MITRE • 10/15/2026
An Improper Release of Memory Before Removing Last Reference vulnerability in the l2cpd process of Juniper Networks Junos OS and Junos OS Evolved platforms allows an adjacent unauthenticated attacker to cause l2cpd memory exhaustion and Layer 2 control-plane disruption via LLDP traffic when fast receive processing is enabled.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 10/15/2026
The identified vulnerability represents a critical flaw within the Link Layer Discovery Protocol daemon, known as l2cpd, which operates on Juniper Networks Junos OS and Junos OS Evolved platforms. This specific defect falls under the category of Improper Release of Memory Before Removing Last Reference, commonly associated with CWE-416 in industry-standard classification systems. The core technical issue arises from a race condition or logic error where memory allocated for processing Link Layer Discovery Protocol packets is not correctly freed before the final reference to that memory block is removed. This mismanagement leads directly to memory exhaustion within the l2cpd process, as leaked memory accumulates over time with each processed packet until system resources are depleted.
The operational impact of this vulnerability is severe and immediate for network infrastructure relying on Layer 2 control plane functions. An adjacent unauthenticated attacker can exploit this flaw by sending specifically crafted LLDP traffic to the affected device. Because the attack requires only adjacency, it does not necessitate complex routing or authentication bypasses, making it highly accessible to any entity connected to the same broadcast domain. As the l2cpd process consumes increasing amounts of memory due to the leak, its ability to function correctly degrades rapidly. This degradation results in Layer 2 control-plane disruption, which can manifest as instability in spanning tree protocol operations, loss of neighbor discovery capabilities, and potentially a complete crash or restart of the daemon, leading to intermittent connectivity issues for devices on that segment.
From an offensive security perspective, this vulnerability aligns with ATT&CK technique T1498 Network Denial of Service, specifically sub-technique T1498.002 Resource Exhaustion via Flooding. The attacker leverages the fast receive processing feature to amplify the rate at which vulnerable memory allocations occur, accelerating the exhaustion process. This allows for a denial-of-service condition that targets the availability component of the CIA triad without requiring elevated privileges or remote network access beyond local adjacency.
Mitigation strategies must focus on both immediate remediation and long-term architectural adjustments. The primary defense is to apply the vendor-provided software patches that correct the memory management logic within the l2cpd process, ensuring that references are properly decremented before deallocation occurs. In environments where patching cannot be implemented immediately due to operational constraints, network administrators should consider disabling LLDP on interfaces facing untrusted or adjacent networks if it is not strictly required for operations. Additionally, enabling fast receive processing features should be reviewed carefully; while beneficial for performance in trusted segments, this vulnerability highlights the risk of exposing memory-intensive control plane processes to high-volume traffic from potentially hostile sources. Regular monitoring of l2cpd process memory usage can also serve as an early detection mechanism for potential exploitation attempts before a full denial-of-service condition is reached.