CVE-2021-31375Network attack vector

Route spoofing via improperly validated BGP update

Published Oct 19, 2021 · Updated Sep 17, 2024

Improper input validation in Juniper Networks Junos OS allows remote attackers to bypass RPKI checks with a crafted BGP update. The RPD routing daemon mishandles a specific BGP update during origin validation and accepts or propagates a spoofed advertisement instead of enforcing the RPKI policy. Exposure requires BGP origin validation with RPKI to be configured, and exploitation can corrupt routing decisions and redirect traffic.

CVSS severity7.2
High
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Juniper Networks Junos OS allows remote attackers to bypass RPKI checks with a crafted BGP update. The RPD routing daemon mishandles a specific BGP update during origin validation and accepts or propagates a spoofed advertisement instead of enforcing the RPKI policy. Exposure requires BGP origin validation with RPKI to be configured, and exploitation can corrupt routing decisions and redirect traffic.

The record

CVE
CVE-2021-31375
Published
Oct 19, 2021
Updated
Sep 17, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-358, CWE-20, T1565.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 19, 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

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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=12.3 <12.3R12-S18
  2. Affected versionversion=15.1 <15.1R7-S9
  3. Affected versionversion=17.2 <17.2R3-S3
  4. Affected versionversion=17.3 <17.3R3-S7
  5. Affected versionversion=17.4 <17.4R2-S9, 17.4R3
  6. Affected versionversion=18.1 <18.1R3-S13
  7. Affected versionversion=18.2 <18.2R3-S3
  8. Affected versionversion=18.3 <18.3R3-S1
  9. Affected versionversion=18.4 <18.4R3
  10. Affected versionversion=19.1 <19.1R2
  11. Affected versionversion=19.2 <19.2R2
  12. Affected versionversion=19.3 <19.3R2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=12.3 <12.3R12-S18; version=15.1 <15.1R7-S9; version=17.2 <17.2R3-S3; version=17.3 <17.3R3-S7; version=17.4 <17.4R2-S9, 17.4R3; version=18.1 <18.1R3-S13; version=18.2 <18.2R3-S3; version=18.3 <18.3R3-S1; version=18.4 <18.4R3; version=19.1 <19.1R2; version=19.2 <19.2R2; version=19.3 <19.3R2

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
7.2Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:L

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-358Improperly Implemented Security Check for Standard
CWE-20Improper Input Validation
T1565.002Transmitted Data Manipulation

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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