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CVE-2026-102077: Junos OS: MX Series with SPC3: In a source NAT scenario malformed packets will lead to resource leaks and eventually traffic stops
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.3% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-10-14 · updated 2026-10-15
- Weakness: CWE-754
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.
Affected products
- Juniper Junos OS: before 23.2R2-S4; from 23.4 before 23.4R2-S5; from 24.2 before 24.2R2 — fixed in 23.2R2-S4, 23.4R2-S5, 24.2R2
How to fix
Upgrade to a fixed version: Juniper Junos OS 23.2R2-S4, 23.4R2-S5, 24.2R2. Check the vendor advisory for mitigations.
References
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