An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper Networks Junos OS on MX Series allows an unauthenticated, network-based attacker to bypass the configured firewall filter and access the control-plane of the device. On MX platforms with MPC10, MPC11, LC4800 or LC9600 line cards, and MX304, firewall filters applied on a loopback interface lo0.n (where n is a non-0 number) don't get executed when lo0.n is in the global VRF / default routing-instance. An affected configuration would be: user@host# show configuration interfaces lo0 | display set set interfaces lo0 unit 1 family inet filter input <filter-name> where a firewall filter is applied to a non-0 loopback interface, but that loopback interface is not referred to in any routing-instance (RI) configuration, which implies that it's used in the default RI. The issue can be observed with the CLI command: user@device> show firewall counter filter <filter_name> not showing any matches. This issue affects Junos OS on MX Series: * all versions before 23.2R2-S6, * 23.4 versions before 23.4R2-S7, * 24.2 versions before 24.2R2, * 24.4 versions before 24.4R2.
This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 6.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts limited data confidentiality, limited integrity, for affected systems. Impacting 5 products from juniper, from juniper, from juniper and 2 others, organizations running these solutions should prioritize assessment and patching.
Reported in 2026, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.
2026-04-09T22:16:25.803
2026-07-08T03:20:40.993
Analyzed
CVSSv3.1: 6.5 (MEDIUM)
| Type | Vendor | Product | Version/Range | Vulnerable? |
|---|---|---|---|---|
| Operating System | juniper | junos | < 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.2 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 23.4 | Yes |
| Operating System | juniper | junos | 24.2 | Yes |
| Operating System | juniper | junos | 24.2 | Yes |
| Operating System | juniper | junos | 24.2 | Yes |
| Operating System | juniper | junos | 24.4 | Yes |
| Operating System | juniper | junos | 24.4 | Yes |
| Operating System | juniper | junos | 24.4 | Yes |
| Hardware | juniper | lc4800 | - | No |
| Hardware | juniper | mpc10 | - | No |
| Hardware | juniper | mpc11 | - | No |
| Hardware | juniper | mx304 | - | No |
SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For juniper's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.