CVE-2026-33799 in Junos OS
Summary
by MITRE • 07/10/2026
An Out-of-bounds Write vulnerability in the SNMP daemon (snmpd) of Juniper Networks Junos OS and Junos OS Evolved allows an authenticated network-based attacker sending specific valid SNMPv3 queries to trigger a memory leak. Over time, continuous receipt of these queries will result in snmpd process memory exhaustion, resulting in a process crash and restart, impacting the ability to monitor the system via SNMP.
Memory usage can be monitored using the following command:
user@device> show system processes extensive | match snmpd
This issue affects:
Junos OS:
* all versions before 21.2R3-S8; * from 21.4 before 21.4R3-S7; * from 22.1 before 22.1R3-S6; * from 22.2 before 22.2R3-S4; * from 22.3 before 22.3R3-S3; * from 22.4 before 22.4R3-S2; * from 23.2 before 23.2R2; * from 23.4 before 23.4R2.
Junos OS Evolved: * all versions before 21.2R3-S8-EVO; * from 21.4 before 21.4R3-S7-EVO; * all versions of 22.1-EVO, * from 22.2 before 22.2R3-S4-EVO; * from 22.3 before 22.3R3-S3-EVO; * all versions of 22.4-EVO, * from 23.2 before 23.2R2-EVO; * from 23.4 before 23.4R2-EVO.
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Analysis
by VulDB Data Team • 07/10/2026
This vulnerability represents a critical memory management flaw within the SNMP daemon implementation of juniper networks junos operating systems and junos os evolved platforms. The issue manifests as an out-of-bounds write condition that occurs when processing specific valid snmpv3 queries from authenticated attackers. This particular weakness falls under the common weakness enumeration category of cwe-787 out-of-bounds write which represents one of the most dangerous classes of memory corruption vulnerabilities. The vulnerability is particularly concerning because it requires only authentication to exploit, meaning an attacker who has gained network access with valid credentials can leverage this flaw to cause persistent system degradation.
The technical mechanism behind this vulnerability involves the snmpd daemon's insufficient validation of input parameters within snmpv3 request processing. When legitimate snmpv3 queries are received containing crafted data structures, the daemon fails to properly bounds-check array accesses or buffer operations, leading to memory corruption that eventually results in process termination. This type of attack aligns with the mitre att&ck framework under the technique id t1499 disruption of services which targets availability through resource exhaustion and process crashes. The memory leak aspect specifically relates to how the daemon continuously consumes memory resources without proper cleanup or bounds enforcement during processing of maliciously crafted snmpv3 messages.
The operational impact of this vulnerability extends beyond simple service disruption to create a persistent degradation of monitoring capabilities that are fundamental to network operations. As the snmpd process consumes increasing amounts of memory over time, system administrators may observe gradual performance decline before eventual complete service failure. The restart behavior creates additional complications as it interrupts ongoing monitoring activities and may mask other underlying issues during the brief outage period. This vulnerability essentially undermines the reliability of network infrastructure management tools that depend on snmp connectivity for operational visibility.
Organizations affected by this vulnerability must implement immediate mitigation strategies to protect their juniper network infrastructure. The primary recommended solution involves upgrading to patched versions of junos os and junos os evolved as specified in the advisory, with particular attention to version ranges including 21.2r3-s8 through 23.4r2 for both platforms. System administrators should also consider implementing network segmentation and access controls to limit snmpv3 query sources and reduce attack surface exposure. Monitoring for unusual memory consumption patterns in snmpd processes using the provided command interface will help detect exploitation attempts. Additionally, implementing snmpv3 authentication and encryption measures can provide additional layers of defense against unauthorized access to snmp services while the patch deployment occurs.