CVE-2021-0202Network attack vector

Traffic interruption via Trio MPC memory leak

Published Jan 15, 2021 · Updated Sep 17, 2024

Resource exhaustion in Juniper Networks Junos OS allows remote attackers to restart an MPC and interrupt traffic via network events. On MX Series and EX9200 Series systems, CE-side network events leak next-hop memory in a Trio-based MPC when an IRB interface maps to a VPLS instance or bridge domain. The affected hardware and configuration must be present; exhaustion restarts the MPC and interrupts traffic until restoration.

CVSS severity7.5
High
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Juniper Networks Junos OS allows remote attackers to restart an MPC and interrupt traffic via network events. On MX Series and EX9200 Series systems, CE-side network events leak next-hop memory in a Trio-based MPC when an IRB interface maps to a VPLS instance or bridge domain. The affected hardware and configuration must be present; exhaustion restarts the MPC and interrupts traffic until restoration.

The record

CVE
CVE-2021-0202
Published
Jan 15, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-401, CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record 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=17.3R3-S8
  2. Affected versionversion=17.4R3-S2
  3. Affected versionversion=18.2R3-S4 <18.2* changes=[{"at":"18.2R3-S6","status":"unaffected"}]
  4. Affected versionversion=18.3R3-S2 <18.3* changes=[{"at":"18.3R3-S4","status":"unaffected"}]
  5. Affected versionversion=18.4R3-S1 <18.4* changes=[{"at":"18.4R3-S6","status":"unaffected"}]
  6. Affected versionversion=19.2R2 <19.2* changes=[{"at":"19.2R3-S1","status":"unaffected"}]
  7. Affected versionversion=19.4R2 <19.4* changes=[{"at":"19.4R2-S3, 19.4R3","status":"unaffected"}]
  8. Affected versionversion=20.2R1 <20.2* changes=[{"at":"20.2R1-S3, 20.2R2","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.3R3-S8; version=17.4R3-S2; version=18.2R3-S4 <18.2* changes=[{"at":"18.2R3-S6","status":"unaffected"}]; version=18.3R3-S2 <18.3* changes=[{"at":"18.3R3-S4","status":"unaffected"}]; version=18.4R3-S1 <18.4* changes=[{"at":"18.4R3-S6","status":"unaffected"}]; version=19.2R2 <19.2* changes=[{"at":"19.2R3-S1","status":"unaffected"}]; version=19.4R2 <19.4* changes=[{"at":"19.4R2-S3, 19.4R3","status":"unaffected"}]; version=20.2R1 <20.2* changes=[{"at":"20.2R1-S3, 20.2R2","status":"unaffected"}]

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/A:P

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-401Missing Release of Memory after Effective Lifetime
CWE-400Uncontrolled Resource Consumption
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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