CVE-2026-102077 Juniper Networks CVE debrief

Who should care

Defenders responsible for Juniper Networks Junos OS on MX Series with SPC3 should assess exposure and apply updates to prevent potential DoS attacks. This includes verifying exposure on MX Series with SPC3 running Junos OS versions before 23.2R2-S4, 23.4R2-S5, or 24.2R2, and applying vendor-provided updates.

Why it matters

CVE-2026-102077 is a Denial-of-Service (DoS) vulnerability in Junos OS on MX Series with SPC3. Defenders should verify exposure, apply updates, and monitor usage to prevent potential attacks.

• Verify exposure on MX Series with SPC3 running Junos OS versions before 23.2R2-S4, 23.4R2-S5, or 24.2R2
• Apply vendor-provided updates to prevent potential DoS attacks
• Monitor session usage and source NAT resource usage to detect potential issues

Technical summary

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.

Defensive priority

Defenders should prioritize verifying exposure on MX Series with SPC3 running Junos OS versions before 23.2R2-S4, 23.4R2-S5, or 24.2R2, and apply vendor-provided updates.

Recommended defensive actions

• Verify exposure on MX Series with SPC3 running Junos OS versions before 23.2R2-S4, 23.4R2-S5, or 24.2R2
• Apply vendor-provided updates to Junos OS
• Monitor session usage with 'show services sessions summary'
• Monitor source NAT resource usage with 'show services nat pool'
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide details on the vulnerability, affected versions, and potential impact. However, there is limited information on exploitation or victim impact. Defenders should verify exposure on MX Series with SPC3 running Junos OS versions before 23.2R2-S4, 23.4R2-S5, or 24.2R2, and apply vendor-provided updates. The source item provides additional information on the vulnerability and affected versions.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.