CVE-2026-102057 in Junos OS
Summary
by MITRE • 10/14/2026
A Stack-based Buffer Overflow vulnerability in the jdhcpd process of Juniper Networks Junos OS allows an unauthenticated adjacent attacker to cause a denial of service via a DHCP client response. The issue affects DHCP client operation and can interrupt related DHCP, relay, and zero-touch-provisioning services.
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Analysis
by VulDB Data Team • 10/14/2026
The identified vulnerability represents a critical security flaw within the Dynamic Host Configuration Protocol daemon process, known as jdhcpd, in Juniper Networks Junos OS. This specific weakness is classified as a stack-based buffer overflow, which 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 is triggered by an unauthenticated attacker positioned adjacent to the affected device, typically within the same local network segment. The attack vector involves sending a specially crafted DHCP client response packet that exceeds the expected buffer size allocated for processing incoming messages. Because the input validation mechanisms are insufficient, the excessive data overwrites adjacent memory locations on the stack, leading to corruption of critical control data such as return addresses or function pointers. This exploitation technique is directly aligned with Common Weakness Enumeration identifier CWE-121, which defines stack-based buffer overflow vulnerabilities where local variables and execution context are overwritten due to inadequate bounds checking during input processing.
The operational impact of this vulnerability is severe, primarily manifesting as a denial of service condition for the affected device. When the jdhcpd process crashes or behaves unpredictably due to memory corruption, it disrupts essential network services that rely on DHCP operations. Specifically, the integrity of DHCP client functionality is compromised, which can prevent devices from obtaining IP addresses and other configuration parameters automatically. Furthermore, because Junos OS integrates these services deeply into its networking infrastructure, the disruption extends beyond simple address assignment. The failure of jdhcpd can interrupt DHCP relay functions, which are crucial for forwarding DHCP messages between subnets, thereby breaking connectivity in complex network topologies. Additionally, zero-touch provisioning workflows, which rely on automated configuration delivery during device deployment or replacement, may fail entirely if the underlying daemon is unresponsive. This aligns with ATT&CK technique T1498, Network Denial of Service, as the attacker can effectively degrade or halt critical network availability without needing prior authentication credentials.
From a technical perspective, stack-based buffer overflows are particularly dangerous because they allow for potential code execution if an attacker carefully crafts the overflow payload to overwrite return addresses with shellcode pointers. However, in this specific instance involving jdhcpd and DHCP client responses, the primary observed impact is stability-related rather than remote code execution. The lack of authentication required to exploit this flaw makes it especially perilous in environments where untrusted devices or rogue endpoints might be connected to the network segment hosting the Juniper device. Attackers can leverage standard networking tools to generate malformed packets that trigger the overflow, causing the daemon to crash repeatedly and resulting in a persistent denial of service state until the process is manually restarted or the system is rebooted. This scenario highlights the risks associated with services that handle untrusted input from network interfaces without rigorous sanitization and length validation checks prior to buffer allocation.
Mitigation strategies for this vulnerability focus on both immediate remediation and long-term architectural improvements. The most effective countermeasure is to apply the vendor-provided software patches or updates released by Juniper Networks, which address the underlying code defects in jdhcpd that allow the buffer overflow to occur. Administrators should ensure their systems are updated to versions where this specific flaw has been resolved through improved input validation and bounds checking mechanisms. In addition to patching, network segmentation can serve as a defensive layer; restricting DHCP traffic to trusted subnets or implementing access control lists on router interfaces can prevent adjacent unauthenticated attackers from reaching the vulnerable service. Deploying intrusion detection systems that monitor for anomalous DHCP packet sizes may also help in identifying and blocking exploitation attempts before they trigger the overflow condition, thereby preserving network stability while permanent fixes are deployed.