CVE-2021-31367

FPC crash via BGP FlowSpec heap leak

Published Oct 19, 2021 · Updated Sep 16, 2024

A memory leak in the Junos OS PFE on PTX Series routers allows adjacent attackers to crash and restart the FPC with BGP FlowSpec routes. The PFE fails to release heap memory after processing genuine BGP FlowSpec packets, so repeated routes exhaust the FPC heap. BGP FlowSpec must be configured, and continued receipt sustains repeated FPC crashes and forwarding disruption.

CVSS severity6.5
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A memory leak in the Junos OS PFE on PTX Series routers allows adjacent attackers to crash and restart the FPC with BGP FlowSpec routes. The PFE fails to release heap memory after processing genuine BGP FlowSpec packets, so repeated routes exhaust the FPC heap. BGP FlowSpec must be configured, and continued receipt sustains repeated FPC crashes and forwarding disruption.

The record

CVE
CVE-2021-31367
Published
Oct 19, 2021
Updated
Sep 16, 2024
Vendor
Juniper Networks
Product
Junos OS
Classifications
CWE-401, T1499.003
Attack vector
adjacent
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=19.1 <19.1R3-S7
  2. Affected versionversion=19.2 <19.2R1-S7, 19.2R3-S3
  3. Affected versionversion=19.3 <19.3R2-S6, 19.3R3-S3
  4. Affected versionversion=19.4 <19.4R1-S4, 19.4R3-S6
  5. Affected versionversion=20.1 <20.1R2-S2, 20.1R3
  6. Affected versionversion=20.2 <20.2R3-S1
  7. Affected versionversion=20.3 <20.3R3
  8. Affected versionversion=20.4 <20.4R3
  9. Affected versionversion=21.1 <21.1R2
  10. Affected versionversion=unspecified <18.4R3-S9

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Juniper Networks · Junos OSversion=19.1 <19.1R3-S7; version=19.2 <19.2R1-S7, 19.2R3-S3; version=19.3 <19.3R2-S6, 19.3R3-S3; version=19.4 <19.4R1-S4, 19.4R3-S6; version=20.1 <20.1R2-S2, 20.1R3; version=20.2 <20.2R3-S1; version=20.3 <20.3R3; version=20.4 <20.4R3; version=21.1 <21.1R2; version=unspecified <18.4R3-S9

Published CVSS scores

2.9NIST NVDAV:A/AC:M/Au:N/C:N/I:N/A:P
6.5Juniper NetworksCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-401Missing Release of Memory after Effective Lifetime
T1499.003Application Exhaustion Flood

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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