CVE-2024-39540: Juniper Junos

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

An Improper Check for Unusual or Exceptional Conditions vulnerability in the Packet Forwarding Engine (pfe) of Juniper Networks Junos OS on SRX Series, and MX Series with SPC3 allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS). When an affected device receives specific valid TCP traffic, the pfe crashes and restarts leading to a momentary but complete service outage. This issue affects Junos OS: 21.2 releases from 21.2R3-S5 before 21.2R3-S6. This issue does not affect earlier or later releases.

Affected products

• Juniper Junos: version 21.2 only

Published 2024-07-11. Last modified 2026-06-17.