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CVE-2026-57031

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 configure…

Published Jul 9, 2026CWE-754EPSS 0.22%

Overview

CVE-2026-57031 is a medium-severity vulnerability. It was published on July 9, 2026 and has a CVSS 3.1 base score of 4.7 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 4.7, rated MEDIUM. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refsupportportal.juniper.net/JSA110091

How CyberStrike helps

Frequently asked questions

What is CVE-2026-57031?

CVE-2026-57031 is a medium-severity vulnerability. It was published on July 9, 2026 and has a CVSS 3.1 base score of 4.7 (MEDIUM).

How severe is CVE-2026-57031?

This vulnerability has a CVSS 3.1 base score of 4.7, rated MEDIUM. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-57031?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-57031?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-57031 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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