Juniper Junos OS up to 24.4R0/24.4R1/25.2R1-S1/25.2R1 Packet Forwarding Engine unusual condition

Summaryinfo

A vulnerability, which was classified as critical, has been found in Juniper Junos OS up to 24.4R0/24.4R1/25.2R1-S1/25.2R1. The impacted element is an unknown function of the component Packet Forwarding Engine. The manipulation leads to unusual condition. This vulnerability is listed as CVE-2026-33781. The attack must be carried out from within the local network. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Juniper Junos OS up to 24.4R0/24.4R1/25.2R1-S1/25.2R1 and classified as critical. This issue affects an unknown functionality of the component Packet Forwarding Engine. The manipulation with an unknown input leads to a unusual condition vulnerability. Using CWE to declare the problem leads to 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. Impacted is 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 specific EX and QFX Series devices allow an unauthenticated, adjacent attacker to cause a complete Denial of Service (DoS). On EX4k, and QFX5k platforms configured as service-provider edge devices, if L2PT is enabled on the UNI and VSTP is enabled on NNI in VXLAN scenarios, receiving VSTP BPDUs on UNI leads to packet buffer allocation failures, resulting in the device to not pass traffic anymore until it is manually recovered with a restart.This issue affects Junos OS: * 24.4 releases before 24.4R2, * 25.2 releases before 25.2R1-S1, 25.2R2. This issue does not affect Junos OS releases before 24.4R1.

The advisory is shared at kb.juniper.net. The identification of this vulnerability is CVE-2026-33781 since 03/23/2026. The exploitation is known to be easy. The attack can only be done within the local network. No form of authentication is needed for a successful exploitation. 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 04/10/2026).

Upgrading to version 24.4R1, 24.4R2, 25.2R1-S1 or 25.2R2 eliminates this vulnerability.

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Productinfo

Type

• Router Operating System

Vendor

• Juniper

Name

• Junos OS

Version

• 24.4R0
• 24.4R1
• 25.2R1
• 25.2R1-S1

License

• commercial

Website

• Vendor: https://www.juniper.net/

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