CVE-2026-101980 in Junos OS
Summary
by MITRE • 10/14/2026
An Integer Underflow vulnerability in the kernel of Juniper Networks Junos OS with Extended Echo configured allows an unauthenticated, network-based attacker to cause a denial of service by a kernel crash.
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Analysis
by VulDB Data Team • 10/14/2026
The identified security flaw resides within the core operating system components of Juniper Networks Junos OS, specifically affecting configurations where the Extended Echo feature is enabled. This vulnerability manifests as an integer underflow condition during the processing of network traffic directed at the affected services. The root cause lies in improper validation or boundary checking when handling numerical values associated with echo request parameters. When a specially crafted packet containing manipulated numeric fields reaches the kernel, it triggers arithmetic operations that result in negative values being stored in unsigned integer variables or memory buffers allocated for smaller sizes than required. This discrepancy leads to incorrect memory access patterns and buffer management errors within the privileged execution context of the operating system kernel.
From an operational perspective, this vulnerability poses a severe risk to network infrastructure stability because it allows unauthenticated attackers to exploit the flaw remotely over standard IP networks. An adversary does not need valid credentials or prior access to the device; they can simply send maliciously crafted packets from any reachable host on the network segment. The immediate consequence of exploiting this integer underflow is a kernel panic, which results in an abrupt system crash and subsequent denial of service for all services hosted on the Juniper device. This disruption affects not only the targeted router or firewall but also potentially impacts connected networks that rely on routing protocols or security policies enforced by the compromised device, leading to significant downtime and potential data loss during recovery periods.
In terms of threat classification, this vulnerability aligns with CWE-192, which describes integer coercion errors where a value is incorrectly converted from one numeric type to another, often resulting in unexpected behavior such as underflows or overflows. Furthermore, the exploitation technique falls under MITRE ATT&CK tactic T1499, specifically Endpoint Denial of Service, as it aims to degrade or halt system availability through resource exhaustion via kernel-level crashes rather than consuming CPU cycles directly. The attack vector is classified as Network-based with no additional privileges required for the attacker, highlighting its high severity and ease of exploitation in environments where such devices are exposed to untrusted networks without adequate ingress filtering.
Mitigation strategies must focus on both immediate remediation and long-term architectural improvements. Juniper Networks has likely released specific software patches or version updates that address the underlying code logic responsible for the integer underflow; applying these vendor-provided fixes is the primary defense mechanism. Administrators should verify their current Junos OS version against official security advisories to determine if they are running a vulnerable release and upgrade immediately upon availability of a patched build. In addition to patching, network-level controls such as Access Control Lists (ACLs) can be deployed at perimeter firewalls or routers to restrict access to the Extended Echo service from untrusted sources, effectively reducing the attack surface by blocking malicious traffic before it reaches the vulnerable kernel component. Regular vulnerability scanning and configuration audits should also be implemented to ensure that unnecessary services like Extended Echo are disabled if not explicitly required for operational needs, thereby minimizing potential entry points for attackers seeking to disrupt network availability.