CVE-2026-57031: 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

mediumCVSS 4.7CVE-2026-57031

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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: medium — CVSS 4.7
Published: 2026-07-09
Last updated: 2026-07-10
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-57031

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-570310.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-57031	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[NEW] [high] Juniper JUNOS and JUNOS Evolved: Multiple vulnerabilitiescert-bund
unknownJuniper Junos OS Multiple Vulnerabilitieshkcert
unknownMultiple vulnerabilities in Juniper Networks products (July 09, 2026)cert-fr-avis

Recent advisories for An Improper Check

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

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