CVE-2021-1588Network attack vector

Device reload via malformed MPLS OAM packets

Published Aug 25, 2021 · Updated Nov 7, 2024

Denial of service in Cisco NX-OS Software allows remote attackers to reload affected switches via malformed MPLS OAM packets. The MPLS OAM packet handler improperly validates crafted echo-request or echo-reply packets, causing the OAM process to crash and restart repeatedly. Exploitation requires MPLS OAM to be enabled and packets to reach an MPLS-forwarding interface from the same MPLS domain or under specific forwarding conditions.

CVSS severity8.6
High
EPSS probability1.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Cisco NX-OS Software allows remote attackers to reload affected switches via malformed MPLS OAM packets. The MPLS OAM packet handler improperly validates crafted echo-request or echo-reply packets, causing the OAM process to crash and restart repeatedly. Exploitation requires MPLS OAM to be enabled and packets to reach an MPLS-forwarding interface from the same MPLS domain or under specific forwarding conditions.

The record

CVE
CVE-2021-1588
Published
Aug 25, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco NX-OS Software
Classifications
CWE-20, CWE-126, CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 25, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 7, 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=n/a

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ClamAV · Cisco NX-OS Softwareversion=n/a

Published CVSS scores

5.0NISTAV:N/AC:L/Au:N/C:N/I:N/A:P
8.6Cisco Systems, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/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.

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-20Improper Input Validation
CWE-126Buffer Over-read
CWE-125Out-of-bounds Read
T1499.004Application or System Exploitation

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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