Description
An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with SPC3 allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).



On MX Series with SPC3 line-card and source NAT configuration, when a specific malformed IPv6 packet is received, it is not dropped but instead a session is created and NAT resources are allocated. Continued receipt of such packets will eventually lead to session or resource exhaustion, which will impact all traffic through the device. To recover the device needs to be rebooted.
To monitor session usage, use the following:

show services sessions summary

To monitor source NAT resource usage, use the following: 

show services nat pool

This issue affects Junos OS on MX Series with SPC3:

* All versions before 23.2R2-S4;
* 23.4 versions before 23.4R2-S5;
* 24.2 versions before 24.2R2.
Published: 2026-10-14
Score: 8.7 High
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service
Action: Immediate Patch
AI Analysis

Impact

An improper check for unusual or exceptional conditions in the Packet Forwarding Engine of Junos OS allows a network‑based, unauthenticated attacker to send malformed IPv6 packets in a source NAT scenario. These packets are not dropped; instead a session is created and NAT resources are consumed. Continuous traffic of such packets causes session or resource exhaustion, halting all traffic through the device and forcing a reboot to recover.

Affected Systems

Juniper Networks Junos OS on MX Series with SPC3 line‑cards. Affected versions include all releases before 23.2R2‑S4, all 23.4 releases before 23.4R2‑S5, and all 24.2 releases before 24.2R2. The fix is available in Junos OS 23.2R2‑S4, 23.4R2‑S5, 24.2R2, 24.4R1, and all subsequent releases.

Risk and Exploitability

The vulnerability receives a CVSS score of 8.7, indicating a high severity. EPSS data is not available and the issue is not listed in the CISA KEV catalog. attack vector is network‑based and requires no authentication. Once exploited, the attacker can indefinitely drain NAT and session resources, leading to a denial of service that requires device reboot to resolve. No workaround is provided by the vendor.

Generated by OpenCVE AI on October 15, 2026 at 14:54 UTC.

Remediation

Vendor Solution

The following software releases have been updated to resolve this specific issue: Junos OS: 23.2R2-S4, 23.4R2-S5, 24.2R2, 24.4R1, and all subsequent releases.

Vendor Workaround

There are no known workarounds for this issue.

OpenCVE Recommended Actions

  • Apply a Junos OS release that includes the fix – 23.2R2‑S4, 23.4R2‑S5, 24.2R2, 24.4R1, or any later version.
  • Reboot the device after installing the update to clear any stale NAT or session state.
  • Continuously monitor NAT pool and session usage with "show services nat pool" and "show services sessions summary" to detect anomalous resource consumption.

Generated by OpenCVE AI on October 15, 2026 at 14:54 UTC.

Tracking

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Advisories

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History

Sat, 17 Oct 2026 01:15:00 +0000

Type Values Removed Values Added
First Time appeared Juniper Networks
Juniper Networks junos Os
Vendors & Products Juniper Networks
Juniper Networks junos Os

Thu, 15 Oct 2026 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Wed, 14 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Description An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (PFE) of Juniper Networks Junos OS on MX Series with SPC3 allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). On MX Series with SPC3 line-card and source NAT configuration, when a specific malformed IPv6 packet is received, it is not dropped but instead a session is created and NAT resources are allocated. Continued receipt of such packets will eventually lead to session or resource exhaustion, which will impact all traffic through the device. To recover the device needs to be rebooted. To monitor session usage, use the following: show services sessions summary To monitor source NAT resource usage, use the following:  show services nat pool This issue affects Junos OS on MX Series with SPC3: * All versions before 23.2R2-S4; * 23.4 versions before 23.4R2-S5; * 24.2 versions before 24.2R2.
Title Junos OS: MX Series with SPC3: In a source NAT scenario malformed packets will lead to resource leaks and eventually traffic stops
Weaknesses CWE-754
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:U/RE:M'}

Subscriptions

Juniper Networks Junos Os
cve-icon MITRE

Status: PUBLISHED

Assigner: juniper

Published:

Updated: 2026-10-14T20:26:08.665Z

Reserved: 2026-09-28T17:37:38.548Z

Link: CVE-2026-102077

cve-icon Vulnrichment

Updated: 2026-10-14T20:18:54.055Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-14T18:17:13.460

Modified: 2026-10-15T16:24:19.073

Link: CVE-2026-102077

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-17T01:00:13Z

Weaknesses
  • CWE-754

    Improper Check for Unusual or Exceptional Conditions