CVE-2021-31353Network attack vector

Remote routing service interruption via crafted BGP update

Published Oct 19, 2021 · Updated Sep 16, 2024

Improper exceptional-condition handling in Juniper Networks Junos OS and Junos OS Evolved allows remote attackers to crash RPD. RPD fails to handle an exceptional condition raised while processing a specific crafted BGP update, causing the daemon to terminate and restart. The update must reach a BGP session, and repeated receipt sustains the routing service interruption.

CVSS severity7.5
High
EPSS probability1.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper exceptional-condition handling in Juniper Networks Junos OS and Junos OS Evolved allows remote attackers to crash RPD. RPD fails to handle an exceptional condition raised while processing a specific crafted BGP update, causing the daemon to terminate and restart. The update must reach a BGP session, and repeated receipt sustains the routing service interruption.

The record

CVE
CVE-2021-31353
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS Evolved
Classifications
CWE-755, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 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=21.1-EVO <21.1R2-EVO
  2. Affected versionversion=21.2-EVO <21.2R2-EVO
  3. Affected versionversion=unspecified <20.4R2-S3-EVO, 20.4R3-EVO

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OS Evolvedversion=21.1-EVO <21.1R2-EVO; version=21.2-EVO <21.2R2-EVO; version=unspecified <20.4R2-S3-EVO, 20.4R3-EVO
Juniper Networks · Junos OSversion=19.3R3-S2; version=19.4R3-S3; version=21.1 <21.1R2

Published CVSS scores

7.5Juniper Networks, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0National 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-755Improper Handling of Exceptional Conditions
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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