CVSS: v3.1: 4.7 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N)CVSS: v4.0: 5.3 (CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/AU:Y/RE:M)
An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (PFE) of Juniper Networks Junos OS on MX Series allows adjacent subscribers to bypass configured firewall filters.
On MX Series devices with MPC10/11, LC4800/9600, and MX304 with subscribers configured on static interfaces, ingress firewall filters are not enforced, so that neither protocol level nor upstream bandwidth limitation are in effect.
This issue affects Junos OS on MX with MPC10/11, LC4800/9600/4802, and MX304:
To be exposed to this issue a configuration for static subscribers with an input filter is required:[ system services static-subscribers ][ dynamic-profiles <profile-name> interfaces <interface> unit <unit> family (inet|inet6) filter input <filter-name> ]
Juniper SIRT is not aware of any malicious exploitation of this vulnerability.
This issue was seen during production usage.
This issue has been assigned CVE-2026-57031.
The following software releases have been updated to resolve this specific issue: Junos OS: 23.2R2-S7, 23.4R2-S7, 24.2R2-S3, 24.4R2-S2, 25.2R2, 25.4R1, and all subsequent releases.
This issue is being tracked as 1902909 which is visible on the Customer Support website.
Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).
There are no known workarounds for this issue.
2026-07-08: Initial Publication