CVE-2026-57031

Adjacent firewall-filter bypass via static subscribers

Published Jul 9, 2026 · Updated Jul 9, 2026

Improper condition handling in affected Juniper Networks Junos OS releases on MX Series allows attackers to bypass ingress firewall filters. The packet forwarding engine fails to enforce configured input filters for static-subscriber traffic, leaving protocol restrictions and upstream bandwidth limits inactive. Exploitation requires an adjacent subscriber, a static-subscriber input filter, and affected MX304 or MX Series forwarding hardware.

CVSS severity5.3
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper condition handling in affected Juniper Networks Junos OS releases on MX Series allows attackers to bypass ingress firewall filters. The packet forwarding engine fails to enforce configured input filters for static-subscriber traffic, leaving protocol restrictions and upstream bandwidth limits inactive. Exploitation requires an adjacent subscriber, a static-subscriber input filter, and affected MX304 or MX Series forwarding hardware.

The record

CVE
CVE-2026-57031
Published
Jul 9, 2026
Updated
Jul 9, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-754, T1562.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=23.2R2-S1 <23.2R2-S7
  2. Affected versionversion=23.4R2 <23.4R2-S7
  3. Affected versionversion=24.2 <24.2R2-S3
  4. Affected versionversion=24.4 <24.4R2-S2
  5. Affected versionversion=25.2 <25.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=23.2R2-S1 <23.2R2-S7; version=23.4R2 <23.4R2-S7; version=24.2 <24.2R2-S3; version=24.4 <24.4R2-S2; version=25.2 <25.2R2

Published CVSS scores

4.7Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
5.3Juniper NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1562.004Impair Defenses: Disable or Modify System Firewall

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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