CVE-2026-21913Network attack vector

Unauthenticated service outage via traffic-induced FXPC crash

Published Jan 15, 2026 · Updated Jan 15, 2026

Improper resource initialization in Junos OS allows remote attackers to crash EX4000 switching via high-volume traffic. The Internal Device Manager on EX4000-48T, EX4000-48P, and EX4000-48MP switches mishandles resource initialization under sustained device-destined traffic, triggering an FXPC watchdog panic and restart. No authentication or user interaction is required, and sufficient traffic causes a complete service outage until the switch automatically restarts.

CVSS severity8.7
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper resource initialization in Junos OS allows remote attackers to crash EX4000 switching via high-volume traffic. The Internal Device Manager on EX4000-48T, EX4000-48P, and EX4000-48MP switches mishandles resource initialization under sustained device-destined traffic, triggering an FXPC watchdog panic and restart. No authentication or user interaction is required, and sufficient traffic causes a complete service outage until the switch automatically restarts.

The record

CVE
CVE-2026-21913
Published
Jan 15, 2026
Updated
Jan 15, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-1419, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=24.4 <24.4R2
  2. Affected versionversion=25.2 <25.2R1-S2, 25.2R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=24.4 <24.4R2; version=25.2 <25.2R1-S2, 25.2R2

Published CVSS scores

8.7Juniper NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1419Incorrect Initialization of Resource
T1498Network Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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