CVE-2021-0270Network attack vector

FPC restart via inline-jflow use-after-free race

Published Apr 22, 2021 · Updated Sep 16, 2024

Use-after-free in the PFE microkernel in Juniper Networks Junos OS 18.1R2 through 18.1R3-S9 allows remote attackers to restart FPCs. Juniper identifies a use-after-free race in PFE microkernel handling but does not disclose the freed object or precise code path. Reachability requires inline-jflow plus concurrent high-volume flows or routing reconvergence; repeated FPC restarts disrupt traffic during core generation.

CVSS severity7.5
High
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the PFE microkernel in Juniper Networks Junos OS 18.1R2 through 18.1R3-S9 allows remote attackers to restart FPCs. Juniper identifies a use-after-free race in PFE microkernel handling but does not disclose the freed object or precise code path. Reachability requires inline-jflow plus concurrent high-volume flows or routing reconvergence; repeated FPC restarts disrupt traffic during core generation.

The record

CVE
CVE-2021-0270
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-362, CWE-416, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 22, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=18.1R2 <18.1* changes=[{"at":"18.1R3-S10","status":"affected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=18.1R2 <18.1* changes=[{"at":"18.1R3-S10","status":"affected"}]

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9NIST NVDCVSS:3.1/AV:N/AC:H/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-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
CWE-416Use After Free
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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