CVE-2026-102056 in Junos OS
Summary
by MITRE • 10/14/2026
An Out-of-bounds Read vulnerability in the cfmd process of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent-network attacker to crash the daemon and disclose limited process memory via a specific CFM Message sent to a configured interface.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability represents a critical security flaw within the Connectivity Fault Management (CFM) implementation of Juniper Networks Junos Operating System and Junos OS Evolved, specifically affecting the cfmd daemon. This Out-of-bounds Read issue stems from improper validation of input data received via CFM messages destined for configured interfaces on affected devices. The core technical failure lies in the application's inability to correctly verify buffer boundaries when processing specific malformed or crafted CFM protocol packets. When an attacker sends a specially constructed message, the cfmd process attempts to read memory locations that fall outside the allocated buffer space, leading to undefined behavior within the operating system's execution environment.
From an operational perspective, this vulnerability allows for two distinct and severe consequences: denial of service and information disclosure. The immediate impact is the crash or restart of the cfmd daemon, which disrupts network connectivity monitoring functions dependent on CFM protocols such as Continuity Check Messages (CCMs) and Link Trace messages. This disruption can lead to temporary loss of visibility into network health and potential instability in services relying on accurate fault detection mechanisms. Furthermore, because the vulnerability involves an out-of-bounds read, it enables an unauthenticated attacker adjacent to the target device to extract limited portions of process memory. This disclosure may reveal sensitive internal state information, configuration details, or other data structures that could facilitate further exploitation against the network infrastructure.
The attack vector is particularly concerning due to its low barrier to entry and high impact profile. The requirement for authentication is absent, meaning any host on the same local area network segment can attempt this exploit without prior credentials. This aligns with common threat models where an attacker gains physical or logical access to a LAN segment adjacent to critical infrastructure devices. The exploitation relies solely on sending specific CFM messages over Layer 2 networks, making it difficult to detect using standard perimeter security controls that do not inspect internal network traffic at the data link layer.
In terms of industry classification standards, this vulnerability maps directly to CWE-125: Out-of-bounds Read, which describes situations where a program reads memory beyond the intended buffer boundary. Additionally, from an offensive cybersecurity framework perspective, it aligns with MITRE ATT&CK techniques related to Discovery and Impact categories, specifically those involving process manipulation or data exfiltration through local network interactions. The ability to crash services corresponds to impact-focused tactics aimed at disrupting availability, while the memory disclosure supports reconnaissance activities that aid in deeper penetration of the target environment.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. Juniper Networks has released software updates addressing this specific flaw within the cfmd process; administrators should prioritize applying these patches to all affected devices as soon as possible. In environments where patching is not immediately feasible, network segmentation becomes critical. Restricting access to CFM-enabled interfaces by implementing strict Access Control Lists (ACLs) that limit traffic sources to only trusted management stations can significantly reduce the attack surface. Additionally, enabling logging for CFM protocol anomalies may help in detecting attempted exploitation activities before they result in service disruption or data leakage. Regular audits of network configuration and continuous monitoring for unusual daemon restart patterns are essential components of a defense-in-depth strategy against this type of vulnerability.