CVE-2026-102046 in Junos OS
Summary
by MITRE • 10/14/2026
A Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in netsctp.ko of Juniper Networks Junos OS on MX Series allows an unauthenticated network attacker to cause a denial of service via crafted SCTP network traffic.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability represents a critical flaw within the Stream Control Transmission Protocol (SCTP) implementation found in the netsctp kernel module of Juniper Networks Junos Operating System, specifically affecting MX Series routers. This issue is classified as an infinite loop or a loop with unreachable exit condition, which fundamentally disrupts the normal execution flow of the network processing logic. The root cause lies in the parsing and state machine handling mechanisms for SCTP packets, where specific crafted inputs can trigger a logical error that prevents the termination condition from ever being met. Consequently, the CPU core responsible for processing these packets becomes trapped in an endless cycle, consuming all available computational resources allocated to that process or thread without yielding control back to the operating system scheduler.
From a technical perspective, this vulnerability exploits weaknesses in how the SCTP stack validates and processes incoming network traffic. An attacker does not require authentication or prior access to the device; they can initiate the attack remotely by sending specially constructed SCTP packets over the network. These crafted packets are designed to exploit edge cases in the protocol state machine, causing the kernel module to enter a recursive loop that cannot be broken through normal operational means. Because this occurs within the kernel space of the operating system, the impact is severe and immediate. The infinite loop effectively causes a denial of service by exhausting CPU resources on the affected MX Series device. This leads to packet loss for legitimate traffic passing through the router, increased latency, and potentially a complete crash or reboot of the network infrastructure if the watchdog timers fail to recover the hung process.
The operational impact of this vulnerability is significant for organizations relying on Juniper MX series equipment for critical routing functions. A successful exploitation results in a service outage that can disrupt business continuity, block access to hosted services, and impair inter-network connectivity. Since the attack vector requires only network reachability, it poses a substantial risk to any internet-facing interface or internal segment where SCTP traffic is permitted. The lack of authentication requirement makes this vulnerability particularly dangerous as it can be exploited by malicious actors anywhere on the connected network without needing credentials or prior compromise of other systems. This aligns with common attack patterns observed in real-world scenarios where attackers target protocol implementations to degrade service availability rather than seeking data exfiltration at this stage.
In terms of industry standard classifications, this vulnerability is categorized under CWE-835, which denotes a loop that always iterates infinitely due to an unreachable exit condition. This classification highlights the logical error in the code structure where the termination criteria are either missing or incorrectly defined for certain input states. Furthermore, from a tactical perspective, this exploit maps directly to MITRE ATT&CK technique T1499, specifically Endpoint Denial of Service via resource exhaustion. The attacker leverages the infinite loop to consume system resources, thereby denying service to legitimate users and processes. Understanding these mappings is crucial for security teams as it helps in identifying similar vulnerabilities across other network devices and informs the prioritization of remediation efforts based on established threat intelligence frameworks.
Mitigation strategies must focus primarily on applying vendor-provided software updates that patch the underlying code flaw within the netsctp module. Juniper Networks typically releases patches or minor version upgrades to address such kernel-level issues, so administrators should verify their current software version against known vulnerable versions and apply the latest recommended release as soon as possible. In environments where immediate patching is not feasible due to maintenance windows or operational constraints, network segmentation becomes a vital compensating control. Restricting SCTP traffic at firewall boundaries by blocking unnecessary inbound connections can significantly reduce the attack surface. Additionally, implementing ingress filtering rules that drop malformed packets before they reach the routing engine can provide an additional layer of defense against crafted payloads designed to trigger this infinite loop condition.