PT-2026-31801 · Juniper Networks · Qfx5K+4

Published 2026-04-09 · Updated 2026-04-09 · CVE-2026-33781

Positive Technologies (AI Summary)

CVSS v3.1

6.5

Medium

Base vector

AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Name of the Vulnerable Software and Affected Versions Juniper Networks Junos OS versions prior to 24.4R2, and 25.2 releases before 25.2R1-S1 and 25.2R2.

Description A flaw exists in the packet forwarding engine (pfe) of Juniper Networks Junos OS on EX and QFX Series devices. An unauthenticated, adjacent attacker can trigger a Denial of Service (DoS). Specifically, on EX4k and QFX5k platforms configured as service-provider edge devices with L2PT enabled on the UNI and VSTP enabled on NNI in VXLAN scenarios, receiving VSTP BPDUs on UNI causes packet buffer allocation failures, leading to a complete loss of traffic until manual recovery via restart.

Recommendations Update to Junos OS version 24.4R2 or later. Update to Junos OS version 25.2R1-S1 or later. Update to Junos OS version 25.2R2 or later.

Fix

Improper Check for Exceptional Conditions

Weakness Enumeration

CWE-754

Related Identifiers

CVE-2026-33781

Affected Products

E-Series

Ex4K

Junos

Qfx Series

Qfx5K

References · 3

• https://kb.juniper.net/JSA107869 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-33781 · Security Note
• https://twitter.com/CVEnew/status/2042364292029116417 · Twitter Post