CVE-2026-102012 in Junos OS
Summary
by MITRE • 10/14/2026
A Reachable Assertion vulnerability in the na-grpcd process of Juniper Networks Junos OS Evolved allows a remote unauthenticated attacker to cause a denial of service via a gRPC telemetry subscription request.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability resides within the na-grpcd daemon, which is responsible for handling gRPC-based network automation and telemetry subscriptions in Juniper Networks Junos OS Evolved environments. This specific flaw manifests as a reachable assertion failure triggered by specially crafted input during the processing of gRPC telemetry subscription requests. In software engineering terms, an assertion is typically used to verify that certain conditions hold true at runtime; when these conditions are violated, the program terminates abruptly rather than handling the error gracefully. Because this vulnerability allows for remote unauthenticated access, any external actor capable of establishing a connection to the affected service can exploit this logic flaw without needing valid credentials or prior authentication tokens.
From a technical perspective, the root cause lies in insufficient input validation and boundary checking within the gRPC message parsing routines of the na-grpcd process. When an attacker sends a malformed telemetry subscription request that violates internal assumptions about data structure integrity or expected parameter ranges, the application fails to sanitize or reject the invalid payload before it reaches critical code paths protected by assertions. Instead of returning a standard error response indicating bad input format, the system triggers a fatal exception leading to the immediate termination of the daemon process. This behavior indicates a lack of robust defensive programming practices where edge cases and maliciously crafted inputs are not adequately accounted for during development or testing phases.
The operational impact of this vulnerability is significant due to its potential to cause a denial of service against network management infrastructure. Since na-grpcd is often central to automated monitoring, configuration distribution, and telemetry collection in modern SDN architectures, crashing this process can disrupt critical network operations. Administrators may lose the ability to push configurations via gRPC channels or receive real-time performance data from devices. In high-availability setups where redundancy relies on specific control plane processes remaining active, the crash of na-grpcd could lead to temporary service degradation or require manual intervention to restart the daemon and restore full functionality. This directly impacts availability, one of the core pillars of information security confidentiality, integrity, and availability triad.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-617: Reachable Assertion, which describes situations where an assertion can be triggered by external input leading to application termination. Furthermore, in terms of tactical classification under the MITRE ATT&CK framework, this exploit technique falls under Initial Access and Execution phases, specifically leveraging service vulnerabilities for remote code execution or denial of service scenarios such as T1498 Network Denial of Service. The unauthenticated nature of the attack vector makes it particularly dangerous as it does not require lateral movement or privilege escalation to initiate the disruption.
Mitigation strategies should prioritize immediate patching if a vendor-supplied fix is available, ensuring that Junos OS Evolved versions are updated to include corrections for this assertion handling logic. In environments where patches cannot be applied immediately, network segmentation and access control lists (ACLs) restricting gRPC traffic ports to trusted management subnets can significantly reduce the attack surface by preventing unauthenticated remote hosts from reaching the vulnerable service. Additionally, deploying intrusion prevention systems capable of detecting anomalous gRPC payloads or malformed subscription requests may provide an additional layer of defense against exploitation attempts until permanent remediation is implemented.