CVE-2024-39556 in Junos OS
Summary
by MITRE • 07/11/2024
A Stack-Based Buffer Overflow vulnerability in Juniper Networks Junos OS and Juniper Networks Junos OS Evolved may allow a local, low-privileged attacker with access to the CLI the ability to load a malicious certificate file, leading to a limited Denial of Service (DoS) or privileged code execution.
By exploiting the 'set security certificates' command with a crafted certificate file, a malicious attacker with access to the CLI could cause a crash of the command management daemon (mgd), limited to the local user's command interpreter, or potentially trigger a stack-based buffer overflow.
This issue affects:
Junos OS:
* All versions 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 23.4R1-S1, 23.4R2;
Junos OS Evolved:
* All versions before 21.4R3-S7-EVO, * from 22.1-EVO before 22.1R3-S6-EVO, * from 22.2-EVO before 22.2R3-S4-EVO, * from 22.3-EVO before 22.3R3-S3-EVO, * from 22.4-EVO before 22.4R3-S2-EVO, * from 23.2-EVO before 23.2R2-EVO, * from 23.4-EVO before 23.4R1-S1-EVO, 23.4R2-EVO.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2024-39556 represents a stack-based buffer overflow within Juniper Networks Junos OS and Junos OS Evolved platforms that manifests through improper input validation during certificate handling operations. This flaw specifically impacts the command management daemon mgd which processes certificate-related commands issued via the command line interface. The vulnerability enables a local attacker with low-privileged access to execute malicious code by exploiting the set security certificates command with a specially crafted certificate file, potentially leading to system instability or unauthorized privilege escalation. The buffer overflow occurs when the system fails to properly validate the size of certificate data before copying it into a fixed-size stack buffer, creating an exploitable condition that can be leveraged by malicious actors with legitimate CLI access.
The technical implementation of this vulnerability stems from inadequate bounds checking within the certificate parsing logic of the mgd daemon. When processing certificate files through the set security certificates command, the system does not sufficiently validate the length of input data against predefined buffer limits, resulting in a classic stack-based buffer overflow condition. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is categorized as a critical security weakness in the Common Weakness Enumeration framework. The attack vector requires local access to the command line interface and the ability to execute the specific certificate loading command, making it a local privilege escalation vulnerability that can be particularly dangerous in environments where multiple users have CLI access.
From an operational impact perspective, this vulnerability creates significant risk for Juniper network infrastructure deployments since it can lead to either limited denial of service conditions or more severe privilege escalation scenarios. The DoS impact is limited to the command management daemon crash, which affects only the local user's command interpreter session, but the potential for privilege escalation means that an attacker could gain elevated system privileges to execute arbitrary code with higher privileges. The vulnerability affects multiple release branches of both Junos OS and Junos OS Evolved, spanning from version 21.4R3-S7 through 23.4R2, indicating that the flaw has been present across several major releases and represents a persistent security concern. The impact severity is elevated due to the combination of local access requirements and the potential for privilege escalation, making it a critical concern for network administrators managing Juniper devices.
Security mitigations for this vulnerability should prioritize immediate patching of affected systems with the latest Juniper software releases containing the fix. Organizations should implement strict access controls limiting CLI access to only authorized personnel and establish monitoring procedures to detect potential exploitation attempts. Network segmentation and privilege separation practices should be enforced to minimize the attack surface, ensuring that users with CLI access do not have unnecessary privileges. The vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation', and T1499, covering 'Endpoint Denial of Service', demonstrating how this flaw can be leveraged for both privilege escalation and service disruption. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all affected devices and implement continuous monitoring for suspicious certificate loading activities, as the exploit requires legitimate CLI access to be effective.