CVE-2021-1378Network attack vector

Unauthenticated service interruption via crafted SSH packets

Published Feb 17, 2021 · Updated Nov 8, 2024

Denial of service in Cisco ASR 5000 Series Software 21.9.0 through 21.19.10 allows remote attackers to interrupt device traffic via SSH. A StarOS SSH-service logic error under specific traffic conditions mishandles a series of crafted packets and stops the affected device from processing traffic. No authentication or user interaction is required, and the reported consequence is traffic interruption without data disclosure or modification.

CVSS severity5.3
Medium
EPSS probability1.50%
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 ASR 5000 Series Software 21.9.0 through 21.19.10 allows remote attackers to interrupt device traffic via SSH. A StarOS SSH-service logic error under specific traffic conditions mishandles a series of crafted packets and stops the affected device from processing traffic. No authentication or user interaction is required, and the reported consequence is traffic interruption without data disclosure or modification.

The record

CVE
CVE-2021-1378
Published
Feb 17, 2021
Updated
Nov 8, 2024
Vendor
ClamAV
Product
Cisco ASR 5000 Series Software
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 17, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 8, 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 ASR 5000 Series Softwareversion=n/a

Published CVSS scores

5.3CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:X/RL:X/RC:X
7.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NISTAV: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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
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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