CVE-2021-0225Network attack vector

Firewall policing bypass via rejected filter combinations

Published Apr 22, 2021 · Updated Sep 16, 2024

Improper condition handling in Junos OS Evolved allows remote attackers to bypass stateless firewall policing through affected filters. The kfirewall-agent rejects certain stateless filter configurations that combine the policer action with other options, so the intended filter does not take effect. Exploitation requires an administrator to have committed an affected combination; matching network traffic then escapes the intended policing control.

CVSS severity5.8
Medium
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper condition handling in Junos OS Evolved allows remote attackers to bypass stateless firewall policing through affected filters. The kfirewall-agent rejects certain stateless filter configurations that combine the policer action with other options, so the intended filter does not take effect. Exploitation requires an administrator to have committed an affected combination; matching network traffic then escapes the intended policing control.

The record

CVE
CVE-2021-0225
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-754
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=19.1R1-EVO <unspecified
  2. Affected versionversion=20.3-EVO <20.3R1-S2-EVO, 20.3R2-EVO

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=19.1R1-EVO <unspecified; version=20.3-EVO <20.3R1-S2-EVO, 20.3R2-EVO

Published CVSS scores

5.8Juniper Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

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-754Improper Check for Unusual or Exceptional Conditions

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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