CVE-2026-101981 in Junos OS
Summary
by MITRE • 10/14/2026
A Stack-based Buffer Overflow vulnerability in the routing protocol daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated adjacent LDP peer to cause an rpd crash or execute arbitrary code via a malformed LDP Label Mapping message.
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Analysis
by VulDB Data Team • 10/15/2026
The identified vulnerability represents a critical security flaw within the routing protocol daemon, known as rpd, of Juniper Networks Junos Operating System and Junos OS Evolved platforms. This specific weakness is classified as a stack-based buffer overflow, which occurs when data written to a fixed-size memory location on the call stack exceeds its allocated boundary. In this context, the vulnerability is triggered by the processing of Label Distribution Protocol messages, specifically malformed LDP Label Mapping messages sent from an adjacent peer. The severity of this issue stems from the fact that it allows for remote code execution without requiring any form of authentication or prior interaction with the system beyond network connectivity.
The technical mechanism behind this exploit relies on the improper validation and bounds checking performed by the rpd process when handling incoming LDP traffic. When an attacker sends a specially crafted Label Mapping message, they can inject shellcode or other malicious payloads into the buffer used to parse the protocol data. Because the daemon does not adequately verify the length of the input against the size of the destination stack variable, the excess data overwrites adjacent memory locations on the stack. This overwrite allows an unauthenticated attacker who is a direct neighbor in the LDP adjacency table to control the instruction pointer or return address, thereby hijacking the execution flow of the rpd process.
From an operational perspective, the impact of this vulnerability is severe and multifaceted. The immediate consequence can be a denial of service condition where the routing protocol daemon crashes, leading to a loss of routing information and potential network instability for all services dependent on that router's forwarding plane. More critically, if the attacker successfully exploits the buffer overflow to execute arbitrary code, they gain full control over the underlying operating system with the privileges of the rpd process. This can lead to complete compromise of the device, allowing the attacker to pivot into other parts of the network, exfiltrate sensitive data, or establish persistent backdoors for long-term access.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-120, which describes buffer copy without checking size limits, and is further categorized under CWE-787, indicating out-of-bounds write on a stack-based variable. In terms of the MITRE ATT&CK framework, this exploit maps to Tactic TA0004 (Privilege Escalation) and Technique T1203 (Exploitation for Privilege Escalation), as well as potentially T1059 (Command and Scripting Interpreter) if shellcode execution is achieved. The attack vector falls under Initial Access via Network-based Exploitation, specifically leveraging a service that requires only network adjacency rather than user interaction or authentication credentials.
Mitigation strategies must focus on both immediate remediation and long-term architectural hardening. The primary defense is to apply the vendor-provided software patches or updates released by Juniper Networks that address this specific flaw in the rpd component. Until patching can be performed, network segmentation should be enforced to restrict LDP adjacency formation only to trusted peers using access control lists on router interfaces. Additionally, enabling strict input validation mechanisms and deploying intrusion prevention systems capable of detecting anomalous LDP packet structures can provide an additional layer of defense against exploitation attempts in the wild. Regular auditing of routing protocols and monitoring for unusual daemon behavior are also recommended practices to detect potential compromise early.