On Juniper Networks Junos OS devices, a stream of TCP packets sent to the Routing Engine (RE) may cause mbuf leak which can lead to Flexible PIC Concentrator (FPC) crash or the system to crash and restart (vmcore). This issue can be trigged by IPv4 or IPv6 and it is caused only by TCP packets. This issue is not related to any specific configuration and it affects Junos OS releases starting from 17.4R1. However, this issue does not affect Junos OS releases prior to 18.2R1 when Nonstop active routing (NSR) is configured [edit routing-options nonstop-routing]. The number of mbufs is platform dependent. The following command provides the number of mbufs counter that are currently in use and maximum number of mbufs that can be allocated on a platform: user@host> show system buffers 2437/3143/5580 mbufs in use (current/cache/total) Once the device runs out of mbufs, the FPC crashes or the vmcore occurs and the device might become inaccessible requiring a manual restart. This issue affects Juniper Networks Junos OS 17.4 versions prior to 17.4R2-S11, 17.4R3-S2; 18.1 versions prior to 18.1R3-S10; 18.2 versions prior to 18.2R2-S7, 18.2R3-S5; 18.2X75 versions prior to 18.2X75-D41, 18.2X75-D420.12, 18.2X75-D51, 18.2X75-D60, 18.2X75-D34; 18.3 versions prior to 18.3R2-S4, 18.3R3-S2; 18.4 versions prior to 18.4R1-S7, 18.4R2-S4, 18.4R3-S1; 19.1 versions prior to 19.1R1-S5, 19.1R2-S1, 19.1R3; 19.2 versions prior to 19.2R1-S5, 19.2R2; 19.3 versions prior to 19.3R2-S3, 19.3R3; 19.4 versions prior to 19.4R1-S2, 19.4R2. Versions of Junos OS prior to 17.4R1 are unaffected by this vulnerability.
| Software | From | Fixed in |
|---|---|---|
| juniper / junos | 17.4-r1 | 17.4-r1.x |
| juniper / junos | 17.4-r2 | 17.4-r2.x |
| juniper / junos | 18.1-r1 | 18.1-r1.x |
| juniper / junos | 18.2x75 | 18.2x75.x |
| juniper / junos | 18.1-r3 | 18.1-r3.x |
| juniper / junos | 18.1-r2 | 18.1-r2.x |
| juniper / junos | 18.2-r1 | 18.2-r1.x |
| juniper / junos | 17.4-r2-s2 | 17.4-r2-s2.x |
| juniper / junos | 17.4-r1-s1 | 17.4-r1-s1.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 | 17.4-r1-s2 | 17.4-r1-s2.x |
| juniper / junos | 18.3-r2 | 18.3-r2.x |
| juniper / junos | 18.3-r1 | 18.3-r1.x |
| juniper / junos | 17.4-r3 | 17.4-r3.x |
| juniper / junos | 17.4-r2-s1 | 17.4-r2-s1.x |
| juniper / junos | 18.1-r2-s2 | 18.1-r2-s2.x |
| juniper / junos | 18.4-r1 | 18.4-r1.x |
| juniper / junos | 17.4 | 17.4.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 | 18.2x75-d20 | 18.2x75-d20.x |
| juniper / junos | 18.3-r1-s2 | 18.3-r1-s2.x |
| juniper / junos | 18.3 | 18.3.x |
| juniper / junos | 18.4 | 18.4.x |
| juniper / junos | 17.4-r1-s5 | 17.4-r1-s5.x |
| juniper / junos | 18.1-r3-s1 | 18.1-r3-s1.x |
| juniper / junos | 17.4-r1-s7 | 17.4-r1-s7.x |
| juniper / junos | 17.4-r1-s4 | 17.4-r1-s4.x |
| juniper / junos | 18.4-r1-s1 | 18.4-r1-s1.x |
| juniper / junos | 17.4-r2-s3 | 17.4-r2-s3.x |
| juniper / junos | 17.4-r2-s4 | 17.4-r2-s4.x |
| juniper / junos | 17.4-r1-s6 | 17.4-r1-s6.x |
| juniper / junos | 18.3-r1-s3 | 18.3-r1-s3.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 | 18.4-r1-s2 | 18.4-r1-s2.x |
| juniper / junos | 19.1-r1 | 19.1-r1.x |
| juniper / junos | 19.1 | 19.1.x |
| juniper / junos | 17.4-r2-s5 | 17.4-r2-s5.x |
| juniper / junos | 17.4-r2-s6 | 17.4-r2-s6.x |
| juniper / junos | 17.4-r2-s7 | 17.4-r2-s7.x |
| juniper / junos | 19.2-r1 | 19.2-r1.x |
| juniper / junos | 18.4-r2 | 18.4-r2.x |
| juniper / junos | 18.2-r3 | 18.2-r3.x |
| juniper / junos | 18.1-r3-s6 | 18.1-r3-s6.x |
| juniper / junos | 18.1-r3-s7 | 18.1-r3-s7.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 | 18.2x75-d40 | 18.2x75-d40.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 | 18.4-r1-s5 | 18.4-r1-s5.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 | 18.3-r1-s5 | 18.3-r1-s5.x |
| juniper / junos | 18.2-r3-s1 | 18.2-r3-s1.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 | 17.4-r2-s8 | 17.4-r2-s8.x |
| juniper / junos | 18.4-r2-s1 | 18.4-r2-s1.x |
| juniper / junos | 19.3 | 19.3.x |
| juniper / junos | 19.3-r1 | 19.3-r1.x |
| juniper / junos | 19.2 | 19.2.x |
| juniper / junos | 18.4-r2-s2 | 18.4-r2-s2.x |
| juniper / junos | 18.3-r1-s6 | 18.3-r1-s6.x |
| juniper / junos | 18.2x75-d30 | 18.2x75-d30.x |
| juniper / junos | 18.2-r3-s2 | 18.2-r3-s2.x |
| juniper / junos | 18.1-r3-s8 | 18.1-r3-s8.x |
| juniper / junos | 19.2-r1-s3 | 19.2-r1-s3.x |
| juniper / junos | 18.3-r3 | 18.3-r3.x |
| juniper / junos | 19.4-r1 | 19.4-r1.x |
| juniper / junos | 19.3-r2 | 19.3-r2.x |
| juniper / junos | 19.1-r2 | 19.1-r2.x |
| juniper / junos | 18.4-r3 | 18.4-r3.x |
| juniper / junos | 18.4-r2-s3 | 18.4-r2-s3.x |
| juniper / junos | 18.3-r3-s1 | 18.3-r3-s1.x |
| juniper / junos | 18.1-r3-s9 | 18.1-r3-s9.x |
| juniper / junos | 19.3-r2-s1 | 19.3-r2-s1.x |
| juniper / junos | 19.3-r1-s1 | 19.3-r1-s1.x |
| juniper / junos | 19.2-r1-s4 | 19.2-r1-s4.x |
| juniper / junos | 19.4-r1-s1 | 19.4-r1-s1.x |
| juniper / junos | 19.3-r2-s2 | 19.3-r2-s2.x |
| juniper / junos | 19.1-r1-s4 | 19.1-r1-s4.x |
| juniper / junos | 18.4-r1-s6 | 18.4-r1-s6.x |
| juniper / junos | 18.3-r2-s3 | 18.3-r2-s3.x |
| juniper / junos | 18.2-r3-s3 | 18.2-r3-s3.x |
| juniper / junos | 17.4-r3-s1 | 17.4-r3-s1.x |
| juniper / junos | 17.4-r2-s9 | 17.4-r2-s9.x |
| juniper / junos | 17.4-r2-s10 | 17.4-r2-s10.x |
| juniper / junos | 18.2-r3-s4 | 18.2-r3-s4.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.