An Improper Following of Specification by Caller vulnerability in web management (J-Web, Captive Portal, 802.1X, Juniper Secure Connect (JSC) of Juniper Networks Junos OS on SRX Series, EX Series, MX240, MX480, MX960, QFX5120 Series, allows an unauthenticated, network-based attacker, sending genuine traffic targeted to the device to cause the CPU to climb until the device becomes unresponsive. 

Continuous receipt of these packets will create a sustained Denial of Service (DoS) condition.

An indicator of compromise is to review the CPU % of the httpd process in the CLI:

e.g.
  show system processes extensive | match httpd

  PID nobody       52   0   20M    191M select   2   0:01   80.00% httpd{httpd} <<<<< the percentage of httpd usage if high may be an indicator

The following software releases have been updated to resolve this specific issue: Junos OS: 21.4R3-S9, 22.2R3-S5, 22.4R3-S4, 23.2R2-S3, 23.4R2-S3, 24.2R1-S1, 24.2R2, 24.4R1, and all subsequent releases.

This issue is being tracked as 1827265 which is visible on the Customer Support website.

Note: Juniper SIRT's policy is not to evaluate releases which are beyond End of Engineering (EOE) or End of Life (EOL).

There are no known workarounds for this issue.

To reduce the risk of exploitation use authentication when using web management services.