CVE-2026-102086 in Junos OS
Summary
by MITRE • 10/15/2026
A NULL Pointer Dereference vulnerability in the DNS plugin of Juniper Networks Junos OS on SRX Series allows an unauthenticated, network-based attacker to cause a complete Denial-of-Service (DoS).
When multiple DNS queries are received in a single flow session, where one query matches a Security Intelligence (SecIntel) feed and another query is sent for DNS Domain Generation Algorithm (DGA) analysis, an error in processing logging of these asynchronous tasks can lead to an FPC crash. The exact timing conditions are outside an attacker's direct control.
This issue affects Junos OS on SRX Series:
* All versions before 23.2R2-S7.7; * from 23.4 before 23.4R2-S8.13; * from 24.2 before 24.2R2-S5.5; * from 24.4 before 24.4R2-S4; * from 25.2 before 25.2R2-S1; * from 25.4 before 25.4R1-S2.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Domain Name System plugin of Juniper Networks Junos OS, specifically impacting SRX Series firewalls and security gateways. This issue is classified as a NULL Pointer Dereference, which represents a fundamental software defect where an application attempts to access memory at a null address that has not been allocated or initialized properly. In the context of network infrastructure devices like those running Junos OS, such errors can have severe consequences for system stability and availability. The vulnerability allows an unauthenticated attacker operating over the network to trigger this condition remotely without requiring any prior authentication credentials. This characteristic significantly lowers the barrier to entry for malicious actors, enabling them to exploit the flaw simply by sending specific types of traffic to the affected device.
The technical mechanism behind this denial-of-service attack involves a complex interaction between two distinct security features: Security Intelligence feeds and Domain Generation Algorithm analysis. When the firewall processes incoming DNS queries, it may simultaneously evaluate these requests against multiple background tasks. Specifically, if one query matches content within a configured Security Intelligence feed while another concurrent query is being analyzed for patterns indicative of a Domain Generation Algorithm, an error occurs in how logging operations are handled for these asynchronous tasks. The system fails to properly manage the memory references associated with these parallel processing streams, leading to a situation where a pointer remains null when it should contain valid data. This race condition or timing-dependent logic error results in the Firewall Processing Component crashing, effectively causing a complete Denial-of-Service state for the device and any traffic passing through it.
The operational impact of this vulnerability is substantial, as it compromises the availability of critical network security infrastructure. A crash in the FPC leads to service interruption, potentially disrupting all network connectivity managed by that specific SRX Series unit. For organizations relying on these devices for perimeter defense, such an outage can expose internal networks to further attacks or cause significant business disruption due to loss of internet access and inter-site communication. The fact that the exact timing conditions are outside direct attacker control does not diminish the severity; rather, it indicates that repeated attempts or specific network load patterns could reliably trigger the crash over time. This makes the vulnerability particularly dangerous in high-throughput environments where DNS traffic is frequent and varied.
From a classification perspective, this issue aligns with CWE-476, which defines NULL Pointer Dereference as a weakness allowing attackers to cause crashes or potentially execute arbitrary code if memory corruption occurs beyond simple denial of service. In terms of the MITRE ATT&CK framework, this vulnerability facilitates availability impact under techniques related to resource exhaustion and component failure. Attackers can leverage this flaw within broader campaigns aimed at degrading network resilience or creating distractions for other malicious activities. The ability to trigger a system crash remotely without authentication places this exploit firmly in the realm of high-risk vulnerabilities that require immediate attention from security operations teams.
Mitigation strategies primarily involve upgrading the Junos OS software on affected SRX Series devices to versions where the flaw has been corrected. Specifically, administrators should ensure their systems are updated beyond version 23.4R2-S8.13 for the 23.4 branch, or apply patches from later stable releases such as 24.2R2-S5.5 and newer depending on the current deployment baseline. For environments where immediate patching is not feasible due to operational constraints, implementing network-level filtering rules can help mitigate risk by restricting access to DNS services from untrusted sources or limiting the volume of concurrent DNS queries that might trigger the asynchronous processing error. Additionally, monitoring logs for signs of FPC crashes and correlating them with high volumes of mixed Security Intelligence and DGA analysis traffic can aid in detecting active exploitation attempts before a total system failure occurs.