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

published 2026-04-09 7 mo ago modified 2026-10-26 13 d ago also EUVD-2026-21199

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 6%
public exploits: 0; none known

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.

Patch / fix

fixed in 1

Juniper Networks Junos OS 24.4R2, 25.2R1-S1, 25.2R2

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 6 mo ago (2026-04-10)

Exploit prediction

0.17% chance of exploitation in the next 30 days, higher than 6% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.5	CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA	4.0	7.1	CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/RE:M
CNA	4.0	7.1	CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:Y/R:X/V:X/RE:M/U:X

Affected products

Juniper Networks Junos OS

Classification

Weakness

CWE-754 Improper Check for Unusual or Exceptional Conditions

References

kb.juniper.net /JSA107869
vendor-advisory, mitigation

Sources

CVE List CVE-2026-33781
NVD CVE-2026-33781

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary