CVE-2026-57031 — MEDIUM (4.7)

Vulnerability Description

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: * 23.2 versions from 23.2R2-S1 before 23.2R2-S7, * 23.4 versions from 23.4R2 before 23.4R2-S7, * 24.2 versions before 24.2R2-S3, * 24.4 versions before 24.4R2-S2, * 25.2 versions before 25.2R2.

CVSS Score

4.7

MEDIUM

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Attack Vector

ADJACENT_NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

CHANGED

Confidentiality

NONE

Integrity

LOW

Availability

NONE

Related Weaknesses (CWE)

CWE-754

References

https://supportportal.juniper.net/JSA110091

FAQ

What is CVE-2026-57031?

CVE-2026-57031 is a vulnerability with a CVSS score of 4.7 (MEDIUM). 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 f...

How severe is CVE-2026-57031?

CVE-2026-57031 has been rated MEDIUM with a CVSS base score of 4.7/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-57031?

Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.