SB2026050827 - Denial of service in Junos OS VXLAN

Security Bulletin ID SB2026050827

CSH Severity

Medium

Patch available

YES

Number of vulnerabilities 1

Exploitation vector Adjecent network

Highest impact Denial of service

Breakdown by Severity

Low
Medium
High
Critical

Description

This security bulletin contains information about 1 vulnerability.

1) Improper Check for Unusual or Exceptional Conditions (CVE-ID: CVE-2026-33781)

CWE-ID: CWE-754 - Improper Check for Unusual or Exceptional Conditions

CVSSv4: CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green

The vulnerability allows a remote attacker to cause a denial of service.

The vulnerability exists due to improper check for unusual or exceptional conditions in the packet forwarding engine (pfe) when receiving VSTP BPDUs on UNI interfaces in VXLAN scenarios. A remote attacker can send specific control protocol packets to cause a denial of service.

Exploitation requires EX4k or QFX5k platforms configured as service-provider edge devices with L2PT enabled on the UNI and VSTP enabled on NNI.

Remediation

Install update from vendor's website.

References

https://supportportal.juniper.net/s/article/2026-04-Security-Bulletin-Junos-OS-EX-Series-QFX-Series-In-a-VXLAN-scenario-when-specific-control-protocol-packets-are-received-memory-leaks-and-eventually-no-traffic-is-passed-CVE-2026-33781