CVE-2026-102084 in Junos OS
Summary
by MITRE • 10/14/2026
An Improper Validation of Syntactic Correctness of Input vulnerability in the VPN daemon of Juniper Networks Junos OS on SRX Series allows an authenticated, network-based attacker to take complete control of the device.
If an SRX device configured for AutoDiscovery VPN (ADVPN) receives a message from a peer that contains one or more specifically malformed attributes, this will cause a buffer overflow, which can allow remote code execution and therefore allow an attacker to take complete control of the device. To be able to carry out this attack an attacker must either have acquired the shared secret to impersonate a peer or have compromised an existing one, so this attack is considerably difficult.
This issue affects Junos OS on SRX Series:
* All versions before 23.2R2-S7.7; * from 23.4 before 23.4R2-S7; * from 24.2 before 24.2R2-S4; * from 24.4 before 24.4R2-S3; * from 25.2 before 25.2R2; * from 25.4 before 25.4R1-S3.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Juniper Networks Junos OS VPN daemon, specifically affecting SRX Series devices configured for AutoDiscovery VPN functionality. This issue is classified as an Improper Validation of Syntactic Correctness of Input, which aligns with CWE-20 in the Common Weakness Enumeration taxonomy. The core technical failure lies in the application's inability to properly validate and sanitize input data received from peer nodes during the IKEv2 negotiation process for ADVPN tunnels. When a maliciously crafted message containing malformed attributes is transmitted by an attacker, it triggers a buffer overflow condition within the daemon’s memory handling routines. This overflow allows for arbitrary code execution on the affected system, granting the attacker complete control over the device rather than merely causing a denial of service or partial compromise.
From an operational perspective, this vulnerability poses a severe risk to network infrastructure integrity and confidentiality. Successful exploitation enables an authenticated, network-based attacker to execute arbitrary commands with the privileges of the VPN daemon, which typically runs with high-level system access. This capability allows for comprehensive device takeover, facilitating further lateral movement within the protected network segment, exfiltration of sensitive data traversing the encrypted tunnels, or modification of routing policies and firewall rules. The impact is particularly acute because ADVPN is designed to dynamically establish secure connections between remote sites without manual configuration, meaning that any peer capable of initiating such a connection could potentially exploit this flaw if authentication controls are insufficiently robust.
The attack vector for this vulnerability requires the attacker to possess valid credentials or shared secrets used by the VPN peers for mutual authentication. Consequently, while the technical mechanism allows for complete system compromise via remote code execution, the practical difficulty of exploitation is heightened because it necessitates prior access to these cryptographic keys. This requirement places the threat in a category where pre-authentication network-based attacks are not directly feasible without first compromising an existing peer or intercepting and decrypting shared secrets through other means such as credential theft or side-channel analysis. Despite this barrier, the severity remains critical due to the potential for total system compromise once authentication is bypassed or credentials are obtained through secondary vectors like phishing or insider threats.
To mitigate this risk, organizations must ensure that all Juniper SRX Series devices running affected versions of Junos OS are updated to a patched release immediately. The specific fixed versions include 23.2R2-S7.7 and later for the 23.2 branch, 23.4R2-S7 and later for the 23.4 branch, 24.2R2-S4 and later for the 24.2 branch, 24.4R2-S3 and later for the 24.4 branch, 25.2R2 and later for the 25.2 branch, and 25.4R1-S3 and later for the 25.4 branch. In addition to patching, administrators should enforce strict access controls on VPN peer configurations, ensuring that only trusted IP addresses are permitted to initiate ADVPN connections. Implementing network segmentation limits the blast radius of a potential compromise by isolating critical infrastructure from general user networks where credential theft might occur more easily.
Furthermore, monitoring and logging mechanisms should be reviewed to detect anomalous IKEv2 negotiation attempts or unusual traffic patterns that may indicate probing for this vulnerability. Although direct exploitation requires valid credentials, attackers often attempt brute-force attacks against shared secrets before attempting complex buffer overflow exploits. Therefore, enforcing strong, complex pre-shared keys and rotating them regularly reduces the likelihood of an attacker acquiring the necessary authentication material. Aligning with MITRE ATT&CK framework techniques, defenders should monitor for T1078 Valid Accounts as a precursor to potential exploitation attempts involving T1203 Exploitation for Client Execution via IKEv2 protocols. Regular vulnerability scanning and configuration audits against known CVEs are essential components of a defense-in-depth strategy to prevent such high-severity remote code execution vulnerabilities from being leveraged in production environments.