CVE-2026-101966 in Junos OS Evolved
Summary
by MITRE • 10/14/2026
A Use of Externally-Controlled Format String vulnerability in the jti-dialoutd of Juniper Networks Junos OS Evolved allows an authenticated network attacker to cause persistent telemetry dial-out denial of service via a crafted analytics sensor resource submitted through gNMI listener.
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Analysis
by VulDB Data Team • 10/15/2026
The identified vulnerability represents a critical security flaw within the jti-dialoutd component of Juniper Networks Junos OS Evolved, specifically classified as a Use of Externally-Controlled Format String. This type of weakness occurs when an application accepts user-supplied input and uses it directly in format string functions without proper validation or sanitization. In this specific context, the vulnerability is exploitable by an authenticated network attacker who can interact with the gNMI (gRPC Network Management Interface) listener service. The attack vector involves submitting a crafted analytics sensor resource that contains maliciously formatted strings intended to be processed as part of telemetry dial-out operations.
The operational impact of this vulnerability centers on the ability to cause a persistent denial of service condition within the affected system. By exploiting the format string flaw, an attacker can manipulate how the jti-dialoutd process interprets data structures, potentially leading to memory corruption or infinite loops that crash the daemon. Since telemetry dial-out services are essential for network monitoring and management, disrupting this component effectively blinds administrators to real-time network health metrics. The persistence of the denial of service implies that the impact is not transient; it may require a manual restart of the affected process or even a full system reboot to restore normal operations, thereby creating significant operational downtime and hindering incident response capabilities during an active attack.
From a technical perspective, this vulnerability aligns with CWE-134, which covers the use of externally-controlled format strings that can lead to information disclosure, denial of service, or code execution depending on the implementation details. The exploitation relies on the attacker's ability to authenticate and send specific gNMI requests containing payload data designed to trigger the formatting error within the dialout daemon. This highlights a failure in input validation mechanisms where user-controlled data is passed directly into logging or processing functions without ensuring that special characters like percent signs are escaped or handled safely. The use of gNMI as the transport mechanism underscores the risk associated with modern network management interfaces, which often expose powerful administrative capabilities over standard protocols if not properly secured and validated.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Juniper Networks has likely released software updates or patches that address this specific flaw by hardening the jti-dialoutd component against format string attacks. Administrators should apply these vendor-provided fixes as soon as they become available to close the vulnerability window. In addition to patching, network segmentation and access control lists should be reviewed to ensure that only authorized management stations can connect to gNMI listeners. Implementing strict authentication policies and limiting exposure of telemetry services to trusted IP ranges reduces the attack surface significantly. Furthermore, developers should adopt secure coding practices such as using parameterized logging functions instead of direct format string usage, ensuring that all external inputs are validated against expected formats before processing. Regular security audits and penetration testing focused on network management interfaces can help identify similar weaknesses in other components of the operating system ecosystem.