CVE-2026-33781: An Improper Check for Unusual or Exceptional Conditions vulnerability in the packet forwarding engine (pfe) of Juniper…
CVE-2026-33781 · Severity: medium · CVSS 6.5 · Published 2026-04-09
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.
No. Junglewise Threat Intelligence has no report of CVE-2026-33781 being exploited in the wild.
How severe is CVE-2026-33781?
Medium severity, with a CVSS score of 6.5, published 9 April 2026.
Which products and versions are affected?
Juniper Ex4000, Juniper Ex4100, Juniper Ex4100-F, Juniper Ex4100-H and 15 more. The advisory does not name versions.
Is there a fix for CVE-2026-33781?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
Am I affected by CVE-2026-33781?
Check whether you run Juniper Ex4000, Juniper Ex4100, Juniper Ex4100-F or one of the others listed. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.