CVE-2026-102054 in Junos OS
Summary
by MITRE • 10/14/2026
An Improper Handling of Length Parameter Inconsistency vulnerability in L2ALM of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated, adjacent attacker to obtain stale PFE packet memory via VXLAN overlay-ping traffic sent to a local VTEP.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability represents a critical flaw within the Layer 2 Adaptive Learning Module (L2ALM) of Juniper Networks Junos OS and Junos OS Evolved, specifically affecting the processing logic for Virtual Extensible LAN overlay-ping traffic directed at local VTEP endpoints. This security issue stems from an improper handling of length parameter inconsistencies during packet validation routines. When a VXLAN encapsulated ping packet is received by the device, the system fails to adequately verify that the declared payload length aligns with the actual data present in the buffer or correctly bounds the memory access operations associated with parsing the inner Ethernet frame and subsequent layers. This discrepancy creates an opportunity for an attacker who possesses adjacent network connectivity to manipulate these parameters, thereby triggering a state where the Packet Forwarding Engine accesses memory regions beyond their intended scope or retains references to stale memory allocations that have not been properly cleared or reallocated.
From a technical perspective, this flaw is categorized under CWE-20 Improper Input Validation and more specifically aligns with CWE-134 Use of Externally-Controlled Format String or CWE-787 Out-of-bounds Write depending on the exact manifestation in memory management, though the primary vector here involves improper length checking leading to stale data exposure. The vulnerability allows an unauthenticated attacker operating from a neighboring network segment to exploit this logic error by crafting specific VXLAN overlay-ping packets with malformed length fields. By sending these crafted packets to a local VTEP, the attacker can induce the device to process the packet in a way that exposes internal state information or stale PFE packet memory contents back through the response mechanism or via side-channel effects observable on the network. This exposure of stale memory is particularly dangerous as it may contain sensitive operational data, routing tables, session keys, or other proprietary information previously held by the device before being freed or reused for new packets.
The operational impact of this vulnerability is significant due to its potential for remote code execution precursors and severe confidentiality breaches. Although the initial description highlights memory exposure, improper length handling in network processing engines often serves as a precursor to buffer overflow conditions that could allow arbitrary code execution on the control plane or forwarding plane components. Even without full exploitation leading to code execution, the ability to read stale PFE packet memory constitutes a high-severity confidentiality violation under the CIA triad. Attackers can leverage this information for further reconnaissance, mapping network topology, identifying active sessions, or extracting cryptographic material that could compromise ongoing encrypted communications. The requirement for adjacent access limits the attack surface compared to remote exploits over the internet but still poses a substantial risk in enterprise environments where trusted internal networks are often assumed secure and lack rigorous segmentation against such layer-two attacks.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. Juniper Networks has released software updates that address this vulnerability by implementing stricter validation checks for VXLAN packet lengths within the L2ALM module, ensuring that all incoming packets are validated against expected bounds before processing begins. Administrators should immediately apply these vendor-provided patches to all affected devices running vulnerable versions of Junos OS and Junnos OS Evolved. In addition to patching, network segmentation practices should be reviewed to ensure that adjacent attackers cannot easily reach VTEP endpoints with untrusted traffic. Implementing strict access control lists on VXLAN interfaces can help restrict the sources allowed to send overlay-ping or other encapsulated traffic to management planes and forwarding engines. Furthermore, enabling logging for malformed packet drops can aid in detecting attempted exploitation activities, allowing security teams to respond proactively to any suspicious patterns indicative of this specific length parameter abuse.