High severity · published Jan 15, 2026
CVE-2026-21913
Junos OS: EX4000: A high volume of traffic destined to the device leads to a crash and restart
7.5
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 35% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
JO
Junos OS · Juniper
24.4 before 24.4R2; 25.2 before 25.2R1-S2, 25.2R2 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-21913
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-21913
Vendor Advisory
https://kb.juniper.net/JSA106014
Vendor Advisory
https://supportportal.juniper.net/JSA106014
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