Juniper Networks Junos OS up to 21.2R3-S5 on SRX/MX Packet Forwarding Engine unusual condition

Summaryinfo

A vulnerability marked as critical has been reported in Juniper Networks Junos OS up to 21.2R3-S5 on SRX/MX. Impacted is an unknown function of the component Packet Forwarding Engine. This manipulation causes unusual condition. This vulnerability is tracked as CVE-2024-39540. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Juniper Networks Junos OS up to 21.2R3-S5 on SRX/MX. It has been declared as critical. Affected by this vulnerability is an unknown code of the component Packet Forwarding Engine. The manipulation with an unknown input leads to a unusual condition vulnerability. The CWE definition for the vulnerability is CWE-754. The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at supportportal.juniper.net. This vulnerability is known as CVE-2024-39540 since 06/25/2024. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/06/2025).

Upgrading to version 21.2R3-S6 eliminates this vulnerability.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Router Operating System

Vendor

• Juniper Networks

Name

• Junos OS

Version

• 21.2R3-S5

License

• commercial

CPE 2.3info

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• 🔍

CPE 2.2info

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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