# CVE-2024-39540

## Summary

- **CVE ID:** CVE-2024-39540
- **Severity:** HIGH
- **CVSS Score:** 8.7 (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)
- **CWE:** CWE-754
- **Published:** Jul 11, 2024
- **Last Modified:** Mar 13, 2026

## Description

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 Networks — Junos OS (21.2R3-S5)

## References

- [CNA](https://supportportal.juniper.net/JSA83000)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.49%
- **EPSS Percentile:** 40.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._