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Fencer Vulns
high 7.5

CVE-2026-21913 json

Junos OS: EX4000: A high volume of traffic destined to the device leads to a crash and restart

published 2026-01-15 9 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-2688

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 35%
public exploits
0
none known

Summary

An Incorrect Initialization of Resource vulnerability in the Internal Device Manager (IDM) of Juniper Networks Junos OS on EX4000 models allows an unauthenticated, network-based attacker to cause a Denial-of-Service (DoS).

On EX4000 models with 48 ports (EX4000-48T, EX4000-48P, EX4000-48MP) a high volume of traffic destined to the device will cause an FXPC crash and restart, which leads to a complete service outage until the device has automatically restarted.

The following reboot reason can be seen in the output of 'show chassis routing-engine' and as a log message:

reason=0x4000002 reason_string=0x4000002:watchdog + panic with core dump

This issue affects Junos OS on EX4000-48T, EX4000-48P and EX4000-48MP:

* 24.4 versions before 24.4R2, * 25.2 versions before 25.2R1-S2, 25.2R2.

This issue does not affect versions before 24.4R1 as the first Junos OS version for the EX4000 models was 24.4R1.

Patch / fix

  • Juniper Networks Junos OS 24.4R2, 25.2R1-S2, 25.2R2

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
9 mo ago

Exploit prediction

0.41% chance of exploitation in the next 30 days, higher than 35% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L/AU:Y/R:A/RE:M
CNA 4.0 8.7 CVSS:4.0/AV:N/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:A/V:X/RE:M/U:X

Affected products

  • Juniper Networks Junos OS

Classification

Weakness
  • CWE-1419 Incorrect Initialization of Resource
  • CWE-665 Improper Initialization

References

Sources

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.