CVE-2021-0257

Traffic interruption via Trio MPC memory leak

Published Apr 22, 2021 · Updated Sep 17, 2024

Resource exhaustion in Juniper Networks Junos OS on affected MX and EX9200 Series releases allows attackers to restart a Trio MPC. Layer 2 events from a customer-edge device make the MPC leak next-hop memory when an IRB interface is mapped to a VPLS instance or bridge domain. This configuration is required; exhaustion restarts the MPC and temporarily interrupts traffic.

CVSS severity6.5
Medium
EPSS probability0.40%
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 on affected MX and EX9200 Series releases allows attackers to restart a Trio MPC. Layer 2 events from a customer-edge device make the MPC leak next-hop memory when an IRB interface is mapped to a VPLS instance or bridge domain. This configuration is required; exhaustion restarts the MPC and temporarily interrupts traffic.

The record

CVE
CVE-2021-0257
Published
Apr 22, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-400, CWE-401, T1499
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=17.3 <17.3R3-S10
  2. Affected versionversion=17.4 <17.4R3-S3
  3. Affected versionversion=18.2 <18.2R3-S7
  4. Affected versionversion=18.3 <18.3R3-S4
  5. Affected versionversion=18.4 <18.4R3-S6
  6. Affected versionversion=19.2 <19.2R3-S2
  7. Affected versionversion=19.3 <19.3R3-S1
  8. Affected versionversion=19.4 <19.4R2-S2, 19.4R3
  9. Affected versionversion=20.2 <20.2R1-S3, 20.2R2
  10. Affected versionversion=20.3 <20.3R1-S1,, 20.3R2

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.3 <17.3R3-S10; version=17.4 <17.4R3-S3; version=18.2 <18.2R3-S7; version=18.3 <18.3R3-S4; version=18.4 <18.4R3-S6; version=19.2 <19.2R3-S2; version=19.3 <19.3R3-S1; version=19.4 <19.4R2-S2, 19.4R3; version=20.2 <20.2R1-S3, 20.2R2; version=20.3 <20.3R1-S1,, 20.3R2

Published CVSS scores

3.3NIST NVDAV:A/AC:L/Au:N/C:N/I:N/A:P
6.5Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
6.5NIST NVDCVSS: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-400Uncontrolled Resource Consumption
CWE-401Missing Release of Memory after Effective Lifetime
T1499Endpoint 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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