CVE-2021-0236Network attack vector

Routing daemon denial of service via BGP packet

Published Apr 22, 2021 · Updated Sep 16, 2024

Improper exception handling in Juniper Networks Junos OS and Junos OS Evolved allows remote authenticated users to crash and restart RPD. RPD fails to handle a specific BGP packet matching a configured VPNv6 FlowSpec term and terminates instead of safely processing it. Only MP-BGP VPNv6 FlowSpec deployments are exposed, and repeated delivery sustains the routing-service interruption through recurring restarts.

CVSS severity6.5
Medium
EPSS probability0.85%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper exception handling in Juniper Networks Junos OS and Junos OS Evolved allows remote authenticated users to crash and restart RPD. RPD fails to handle a specific BGP packet matching a configured VPNv6 FlowSpec term and terminates instead of safely processing it. Only MP-BGP VPNv6 FlowSpec deployments are exposed, and repeated delivery sustains the routing-service interruption through recurring restarts.

The record

CVE
CVE-2021-0236
Published
Apr 22, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-754, T1499
Attack vector
network
Privileges
authenticated

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=20.3-EVO <20.3R2-EVO

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=20.3-EVO <20.3R2-EVO
Juniper Networks · Junos OSversion=18.4 <18.4R1-S8, 18.4R2-S7, 18.4R3-S7; version=19.1 <19.1R2-S2, 19.1R3-S4; version=19.2 <19.2R1-S6, 19.2R3-S2; version=19.3 <19.3R3-S2; version=19.4 <19.4R2-S4, 19.4R3-S1; version=20.1 <20.1R2, 20.1R3, 20.1R3-EVO; version=20.2 <20.2R2, 20.2R3, 20.2R3-EVO; version=20.3 <20.3R1-S1, 20.3R2, 20.3R2-EVO

Published CVSS scores

6.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
6.8NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:C

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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1499Endpoint Denial of Service

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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