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: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

No analysis available yet.

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.

Tracking

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Advisories

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History

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

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: juniper

Published:

Updated: 2026-10-14T17:14:01.511Z

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

Link: CVE-2026-102077

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

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

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

Link: CVE-2026-102077

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-754

    Improper Check for Unusual or Exceptional Conditions