CVE-2018-0026 in Junos
Summary
by MITRE
After Junos OS device reboot or upgrade, the stateless firewall filter configuration may not take effect. This issue can be verified by running the command: user@re0> show interfaces <interface_name> extensive | match filters" CAM destination filters: 0, CAM source filters: 0 Note: when the issue occurs, it does not show the applied firewall filter. The correct output should show the applied firewall filter, for example: user@re0> show interfaces <interface_name> extensive | match filters" CAM destination filters: 0, CAM source filters: 0 Input Filters: FIREWAL_FILTER_NAME-<interface_name> This issue affects firewall filters for every address family. Affected releases are Juniper Networks Junos OS: 15.1R4, 15.1R5, 15.1R6 and SRs based on these MRs. 15.1X8 versions prior to 15.1X8.3.
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Analysis
by VulDB Data Team • 04/06/2023
This vulnerability represents a critical stateless firewall filter configuration failure in Juniper Networks Junos OS devices that occurs specifically after system reboot or upgrade operations. The issue manifests as a failure in the firewall filter state management mechanism, where the configured filters do not properly activate or take effect in the packet processing pipeline. This represents a fundamental flaw in the network security posture of affected devices, as firewall rules that should control traffic flow become ineffective. The vulnerability affects all address families and impacts the core packet filtering functionality that protects network perimeters and internal segments from unauthorized access and malicious traffic.
The technical root cause lies in the improper handling of firewall filter state during device initialization or upgrade processes. When Junos OS devices restart or undergo software upgrades, the system fails to properly establish or validate the firewall filter configurations within the forwarding plane. This failure results in the absence of expected filter references in the interface configuration output, specifically the missing "Input Filters: FIREWAL_FILTER_NAME-<interface_name>" entries that should appear in the show interfaces command output. The problem is particularly insidious because the system appears to function normally while silently failing to enforce security policies. This behavior creates a false sense of security where administrators believe their firewall rules are active and effective, when in reality network traffic flows are not being properly filtered according to policy.
The operational impact of this vulnerability is severe and potentially catastrophic for network security. Affected devices may allow unauthorized traffic to traverse network segments without proper filtering, creating potential attack vectors for malicious actors who can exploit the bypassed security controls. The vulnerability affects all address families, meaning IPv4, IPv6, and other protocol families are equally compromised, providing attackers with multiple potential entry points. Additionally, the issue affects multiple software versions including 15.1R4, 15.1R5, 15.1R6, and various SRs based on these releases, along with 15.1X8 versions prior to 15.1X8.3, indicating a broad attack surface across different Juniper Junos OS releases. This widespread impact suggests the flaw is deeply embedded in the system's initialization and configuration management processes rather than being isolated to a specific feature or module.
From a cybersecurity perspective, this vulnerability aligns with CWE-691, which addresses insufficient control flow management in security-critical systems. The issue represents a failure in the security configuration validation process where the system does not properly verify that security policies have been correctly applied. This vulnerability also maps to ATT&CK technique T1070.004, which covers "Indicator Removal on Host: File Deletion," though in this case the removal is more subtle as the filters are not properly loaded rather than deleted. Organizations affected by this vulnerability face significant risk of unauthorized network access, data exfiltration, and potential lateral movement within their networks. The lack of visible error indicators makes this vulnerability particularly dangerous as it can persist undetected for extended periods, allowing attackers to establish persistent access while the network security controls remain apparently functional but ineffective.
The recommended mitigations include immediate deployment of Juniper's security patches and firmware updates addressing the specific configuration loading issue. Network administrators should also implement additional monitoring to verify that firewall filters are properly loaded and active after each reboot or upgrade event. Configuration management practices should include verification steps that explicitly check for filter application using commands like show interfaces extensive | match filters, and automated systems should be implemented to detect when filters fail to load properly. Organizations should also consider implementing network segmentation and additional security controls as compensating measures while awaiting patch deployment, since the vulnerability affects the core packet filtering functionality that protects network boundaries. The incident underscores the importance of thorough regression testing during software upgrades and the necessity of validating security policy enforcement after any system maintenance operations.