CVE-2026-102050 in Junos OS
Summary
by MITRE • 10/15/2026
A Stack-based Buffer Overflow vulnerability in the l2cpd daemon of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent attacker to cause a denial of service in Layer 2 control-plane processing via LLDP packets received on an interface configured for LLDP. Repeated triggering may disrupt LLDP and other Layer 2 control protocols across the device.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified involves a critical stack-based buffer overflow within the l2cpd daemon, which is responsible for managing Layer 2 control-plane processes in Juniper Networks Junos OS and Junos OS Evolved environments. This specific flaw arises from improper boundary checking when processing Link Layer Discovery Protocol (LLDP) packets received on interfaces where LLDP functionality is enabled. An attacker positioned as an unauthenticated adjacent entity, such as another device connected to the same local network segment or switch port, can exploit this weakness by crafting and transmitting specially constructed LLDP frames containing oversized or malformed data fields. The l2cpd daemon fails to adequately validate the length of incoming packet payloads before copying them into fixed-size stack buffers, leading to memory corruption when the input exceeds the allocated space.
From a technical perspective, this buffer overflow allows an attacker to overwrite adjacent memory locations on the call stack, potentially overwriting return addresses or function pointers. While the primary observed impact is a denial of service resulting from daemon crashes and subsequent restarts, such vulnerabilities often carry the risk of arbitrary code execution if the attack conditions are precisely met and additional exploitation techniques are applied against other system components. The immediate operational consequence is the disruption of LLDP operations across the affected device. Since LLDP is fundamental for network topology discovery, neighbor identification, and configuration management in many enterprise networks, its failure can lead to significant visibility gaps for network administrators and automation systems that rely on this data for dynamic provisioning or fault detection.
The impact extends beyond simple service interruption because repeated triggering of this vulnerability causes the l2cpd process to crash repeatedly, leading to a denial-of-service condition that affects not only LLDP but potentially other Layer 2 control protocols dependent on the same daemon infrastructure. This instability can cause flapping in network state information and may trigger unnecessary failovers or routing recalculations if higher-layer protocols are indirectly affected by the loss of neighbor adjacency data. The ability to exploit this from an adjacent position means that physical access to the local network segment is sufficient for exploitation, lowering the barrier to entry for malicious actors who have gained foothold within the internal LAN perimeter but lack remote network credentials.
In terms of industry classification standards, this vulnerability aligns with CWE-121, which denotes a stack-based buffer overflow resulting from insufficient bounds checking on user-supplied data during memory copy operations. It also maps to MITRE ATT&CK technique T1498, specifically Network Denial of Service via resource exhaustion or service disruption through protocol abuse. The attack vector is classified as adjacent network access with no authentication requirements, highlighting the risk posed by internal threats and compromised devices within trusted segments that are not protected by perimeter firewalls from local layer-two attacks.
Mitigation strategies primarily involve applying vendor-provided software patches to update the Junos OS or Junos OS Evolved versions to include fixes for this buffer overflow condition. Until patching is feasible, network administrators should consider disabling LLDP on interfaces where it is not strictly necessary to reduce the attack surface. Additionally, implementing strict ingress filtering and rate limiting for LLDP packets at edge switches can help mitigate repeated triggering attempts by untrusted adjacent hosts. Monitoring logs for frequent daemon restarts or errors related to l2cpd can serve as an early detection mechanism for exploitation attempts, allowing security teams to isolate affected segments and investigate potential compromise indicators before widespread service disruption occurs.