CVE-2026-101983 in Junos OS
Summary
by MITRE • 10/14/2026
A Stack-based Buffer Overflow vulnerability in the httpd process of Juniper Networks Junos OS and Junos OS Evolved allows an unauthenticated network attacker to cause remote code execution and denial of service via a J-Web virtual-domain configured.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability represents a critical security flaw within the Apache HTTP server, commonly referred to as httpd, which serves as the backend for Juniper Networks' J-Web management interface in both Junos OS and Junos OS Evolved environments. This specific weakness is classified as a stack-based buffer overflow, a type of memory corruption error that occurs when a program writes more data to a fixed-length block of memory on the call stack than it can hold. In this context, the vulnerability arises from insufficient bounds checking during the processing of HTTP requests directed at virtual domains configured within J-Web. An attacker who is unauthenticated and has network access to the management interface can exploit this flaw by crafting maliciously formatted HTTP packets that contain oversized payloads designed to overwrite adjacent memory locations on the stack.
The technical mechanism behind this exploitation involves manipulating specific input parameters or headers sent to the httpd process associated with a virtual domain. When the server processes these malformed requests, it fails to validate the length of the incoming data against the allocated buffer size. This lack of validation allows an attacker to inject shellcode or other executable instructions into the memory space. By carefully controlling the overflow, the attacker can overwrite critical stack elements such as the return address, thereby redirecting the flow of execution to their injected code. This capability effectively grants the attacker arbitrary code execution privileges within the context of the httpd process, which typically runs with elevated permissions necessary for managing network devices.
The operational impact of this vulnerability is severe and multifaceted. The most critical consequence is remote code execution, allowing an unauthenticated adversary to take full control of the affected device or gain access to sensitive management functions without valid credentials. This compromises the confidentiality, integrity, and availability of the network infrastructure managed by Junos OS. Furthermore, the vulnerability can be leveraged to cause a denial of service condition. Even if successful code execution is not achieved, the buffer overflow may crash the httpd process, rendering the J-Web interface inaccessible and preventing administrators from managing the device through this specific channel. In high-security environments where out-of-band management might also be compromised or unavailable, this disruption can lead to significant operational downtime and hinder incident response efforts.
From a classification perspective, this vulnerability aligns with CWE-120, which denotes Buffer Copy without Checking Size of Input, specifically manifesting as a stack-based buffer overflow. It is further categorized under CWE-787 for Out-of-bounds Write on the stack. In terms of adversary tactics and techniques, this exploit maps to MITRE ATT&CK technique T1190, Exploit Public-Facing Application, where attackers leverage vulnerabilities in internet-facing services to gain initial access. Additionally, depending on how the code execution is utilized post-exploitation, it may relate to T1059 Command and Scripting Interpreter if shell commands are executed directly through the compromised process.
Mitigation strategies must address both immediate remediation and long-term security posture improvements. The primary defense is to apply the vendor-provided software patches or updates released by Juniper Networks that correct the input validation logic within the httpd component for J-Web virtual domains. Organizations should prioritize patching systems exposed to untrusted networks, as this vulnerability allows exploitation without authentication. In scenarios where immediate patching is not feasible due to operational constraints, network segmentation and access control lists (ACLs) should be implemented to restrict HTTP traffic destined for the management interface exclusively from trusted administrative subnets. Additionally, deploying intrusion prevention systems with signatures capable of detecting buffer overflow attempts can provide a layer of defense in depth, although reliance on signature-based detection alone is not recommended given the potential for obfuscation techniques used by advanced attackers. Regular vulnerability scanning and continuous monitoring of J-Web access logs are also essential to detect any attempted exploitation activities early.