When configuring stateless firewall filters in Juniper Networks EX4600 and QFX 5000 Series devices using Virtual Extensible LAN protocol (VXLAN), the discard action will fail to discard traffic under certain conditions. Given a firewall filter configuration similar to: family ethernet-switching { filter L2-VLAN { term ALLOW { from { user-vlan-id 100; } then { accept; } } term NON-MATCH { then { discard; } } when there is only one term containing a 'user-vlan-id' match condition, and no other terms in the firewall filter except discard, the discard action for non-matching traffic will only discard traffic with the same VLAN ID specified under 'user-vlan-id'. Other traffic (e.g. VLAN ID 200) will not be discarded. This unexpected behavior can lead to unintended traffic passing through the interface where the firewall filter is applied. This issue only affects systems using VXLANs. This issue affects Juniper Networks Junos OS on QFX5K Series: 18.1 versions prior to 18.1R3-S7, except 18.1R3; 18.2 versions prior to 18.2R2-S7, 18.2R3-S1; 18.3 versions prior to 18.3R1-S5, 18.3R2-S4, 18.3R3; 18.4 versions prior to 18.4R1-S7, 18.4R2-S1, 18.4R3; 19.1 versions prior to 19.1R1-S5, 19.1R2; 19.2 versions prior to 19.2R1-S5, 19.2R2.
| Software | From | Fixed in |
|---|---|---|
| juniper / junos | 18.1-r1 | 18.1-r1.x |
| juniper / junos | 18.1-r3 | 18.1-r3.x |
| juniper / junos | 18.1-r2 | 18.1-r2.x |
| juniper / junos | 18.1-r3-s4 | 18.1-r3-s4.x |
| juniper / junos | 18.1-r3-s3 | 18.1-r3-s3.x |
| juniper / junos | 18.1-r3-s2 | 18.1-r3-s2.x |
| juniper / junos | 18.1 | 18.1.x |
| juniper / junos | 18.1-r2-s1 | 18.1-r2-s1.x |
| juniper / junos | 18.1-r2-s4 | 18.1-r2-s4.x |
| juniper / junos | 18.1-r2-s2 | 18.1-r2-s2.x |
| juniper / junos | 18.1-r3-s1 | 18.1-r3-s1.x |
| juniper / junos | 18.1-r3-s6 | 18.1-r3-s6.x |
| juniper / junos | 18.2-r2-s5 | 18.2-r2-s5.x |
| juniper / junos | 18.2-r2-s6 | 18.2-r2-s6.x |
| juniper / junos | 18.2-r3 | 18.2-r3.x |
| juniper / junos | 18.2-r1 | 18.2-r1.x |
| juniper / junos | 18.2-r2-s3 | 18.2-r2-s3.x |
| juniper / junos | 18.2-r2-s4 | 18.2-r2-s4.x |
| juniper / junos | 18.2-r1-s4 | 18.2-r1-s4.x |
| juniper / junos | 18.2-r1-s5 | 18.2-r1-s5.x |
| juniper / junos | 18.2-r2 | 18.2-r2.x |
| juniper / junos | 18.2 | 18.2.x |
| juniper / junos | 18.2-r2-s1 | 18.2-r2-s1.x |
| juniper / junos | 18.2-r2-s2 | 18.2-r2-s2.x |
| juniper / junos | 18.2-r1-s3 | 18.2-r1-s3.x |
| juniper / junos | 18.3-r1-s1 | 18.3-r1-s1.x |
| juniper / junos | 18.3-r2 | 18.3-r2.x |
| juniper / junos | 18.3-r1 | 18.3-r1.x |
| juniper / junos | 18.3-r1-s2 | 18.3-r1-s2.x |
| juniper / junos | 18.3 | 18.3.x |
| juniper / junos | 18.3-r1-s4 | 18.3-r1-s4.x |
| juniper / junos | 18.3-r1-s3 | 18.3-r1-s3.x |
| juniper / junos | 18.3-r2-s3 | 18.3-r2-s3.x |
| juniper / junos | 18.3-r2-s1 | 18.3-r2-s1.x |
| juniper / junos | 18.3-r2-s2 | 18.3-r2-s2.x |
| juniper / junos | 18.4-r1-s6 | 18.4-r1-s6.x |
| juniper / junos | 18.4-r1-s5 | 18.4-r1-s5.x |
| juniper / junos | 18.4-r2 | 18.4-r2.x |
| juniper / junos | 18.4-r1-s1 | 18.4-r1-s1.x |
| juniper / junos | 18.4-r1 | 18.4-r1.x |
| juniper / junos | 18.4-r1-s3 | 18.4-r1-s3.x |
| juniper / junos | 18.4-r1-s4 | 18.4-r1-s4.x |
| juniper / junos | 18.4-r1-s2 | 18.4-r1-s2.x |
| juniper / junos | 18.4 | 18.4.x |
| juniper / junos | 19.1-r1 | 19.1-r1.x |
| juniper / junos | 19.1 | 19.1.x |
| juniper / junos | 19.1-r1-s1 | 19.1-r1-s1.x |
| juniper / junos | 19.1-r1-s3 | 19.1-r1-s3.x |
| juniper / junos | 19.1-r1-s2 | 19.1-r1-s2.x |
| juniper / junos | 19.1-r1-s4 | 19.1-r1-s4.x |
| juniper / junos | 19.2 | 19.2.x |
| juniper / junos | 19.2-r1-s3 | 19.2-r1-s3.x |
| juniper / junos | 19.2-r1-s4 | 19.2-r1-s4.x |
| juniper / junos | 19.2-r1-s1 | 19.2-r1-s1.x |
| juniper / junos | 19.2-r1-s2 | 19.2-r1-s2.x |
| juniper / junos | 19.2-r1 | 19.2-r1.x |
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.
Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.
Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.