CVE-2021-31379Network attack vector

PFE service interruption via malformed MAP-E packets

Published Oct 19, 2021 · Updated Sep 16, 2024

Incorrect behavior order in Juniper Networks Junos OS on MX Series allows remote attackers to disable a PFE with malformed tunnel packets. The MAP-E reassembly path processes crafted IPv4 or IPv6 traffic in the wrong order, leaving the affected packet-forwarding engine fabric disabled. Exposure requires an MPC 7/8/9/10/11 card with MAP-E IP reassembly enabled; continued packets sustain the service interruption.

CVSS severity7.5
High
EPSS probability1.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect behavior order in Juniper Networks Junos OS on MX Series allows remote attackers to disable a PFE with malformed tunnel packets. The MAP-E reassembly path processes crafted IPv4 or IPv6 traffic in the wrong order, leaving the affected packet-forwarding engine fabric disabled. Exposure requires an MPC 7/8/9/10/11 card with MAP-E IP reassembly enabled; continued packets sustain the service interruption.

The record

CVE
CVE-2021-31379
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-696, T1498
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=17.2R1 <17.2*
  2. Affected versionversion=17.3 <17.3R3-S9
  3. Affected versionversion=17.4 <17.4R2-S12, 17.4R3-S3
  4. Affected versionversion=18.1 <18.1R3-S11
  5. Affected versionversion=18.2 <18.2R2-S6, 18.2R3-S3
  6. Affected versionversion=18.3 <18.3R2-S4, 18.3R3-S1
  7. Affected versionversion=18.4 <18.4R1-S8, 18.4R2-S5, 18.4R3
  8. Affected versionversion=19.1 <19.1R1-S6, 19.1R2-S2, 19.1R3
  9. Affected versionversion=19.2 <19.2R1-S5, 19.2R2
  10. Affected versionversion=19.3 <19.3R2-S5, 19.3R3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=17.2R1 <17.2*; version=17.3 <17.3R3-S9; version=17.4 <17.4R2-S12, 17.4R3-S3; version=18.1 <18.1R3-S11; version=18.2 <18.2R2-S6, 18.2R3-S3; version=18.3 <18.3R2-S4, 18.3R3-S1; version=18.4 <18.4R1-S8, 18.4R2-S5, 18.4R3; version=19.1 <19.1R1-S6, 19.1R2-S2, 19.1R3; version=19.2 <19.2R1-S5, 19.2R2; version=19.3 <19.3R2-S5, 19.3R3

Published CVSS scores

7.5Juniper NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/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-696Incorrect Behavior Order
T1498Network 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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