CVE-2026-33781 Denial of service in Junos OS

High 7.1 Published 9 Apr 2026 Updated 10 Apr 2026

An unauthenticated adjacent attacker can cause a complete denial of service on specific Juniper switches by sending crafted VSTP BPDUs in VXLAN scenarios.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-33781?

CVE-2026-33781 is a high-severity denial of service vulnerability in Juniper Junos, published on 9 Apr 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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.

Weakness: CWE-754

Which versions are affected by CVE-2026-33781?

It affects 1 product.

Products include Juniper Junos.

How do I fix CVE-2026-33781?

No fix has been published for CVE-2026-33781 yet. Limit exposure of the affected software until one is available.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-33781 being exploited?

There is no known exploitation of CVE-2026-33781 in the wild and no public exploit code.

All Juniper Junos vulnerabilities

Sources

Also known as GHSA-gv4f-m3jw-j3h9.