CVE-2026-0203

Adjacent FPC restart via malformed ICMPv4 header

Published Jan 15, 2026 · Updated Jan 15, 2026

Improper exceptional-condition handling in Juniper Networks Junos OS allows attackers on an adjacent network to crash and restart an FPC via ICMPv4. Packet processing accepts a specifically malformed IPv4 header value in an ICMP packet and fails to handle the resulting exceptional condition, crashing the receiving FPC. No authentication is required, but upstream routers do not forward the malformed packet, so exposure is limited to adjacent networks; ICMPv6 and AFT-based line cards are unaffected.

CVSS severity7.1
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper exceptional-condition handling in Juniper Networks Junos OS allows attackers on an adjacent network to crash and restart an FPC via ICMPv4. Packet processing accepts a specifically malformed IPv4 header value in an ICMP packet and fails to handle the resulting exceptional condition, crashing the receiving FPC. No authentication is required, but upstream routers do not forward the malformed packet, so exposure is limited to adjacent networks; ICMPv6 and AFT-based line cards are unaffected.

The record

CVE
CVE-2026-0203
Published
Jan 15, 2026
Updated
Jan 15, 2026
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-755, T1499.004
Attack vector
adjacent
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=0 <21.2R3-S9
  2. Affected versionversion=21.4 <21.4R3-S10
  3. Affected versionversion=22.2 <22.2R3-S7
  4. Affected versionversion=22.3 <22.3R3-S4
  5. Affected versionversion=22.4 <22.4R3-S5
  6. Affected versionversion=23.2 <23.2R2-S3
  7. Affected versionversion=23.4 <23.4R2-S3
  8. Affected versionversion=24.2 <24.2R1-S2, 24.2R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=0 <21.2R3-S9; version=21.4 <21.4R3-S10; version=22.2 <22.2R3-S7; version=22.3 <22.3R3-S4; version=22.4 <22.4R3-S5; version=23.2 <23.2R2-S3; version=23.4 <23.4R2-S3; version=24.2 <24.2R1-S2, 24.2R2

Published CVSS scores

7.1Juniper NetworksCVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
6.5Juniper NetworksCVSS:3.1/AV:A/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)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-755Improper Handling of Exceptional Conditions
T1499.004Application or System Exploitation

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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