CVE-2021-34735Network attack vector

Service interruption via unthrottled ICMP traffic

Published Oct 6, 2021 · Updated Nov 7, 2024

Denial of service in Cisco ATA 190 Series software allows remote attackers to disable the Ethernet interface with crafted ICMP traffic. The ICMP packet-processing path fails to rate-limit a steady stream of packets addressed to the device, forcing its Ethernet port offline. No authentication or user interaction is required; the web interface becomes unreachable and service remains interrupted until a manual power cycle.

CVSS severity8.6
High
EPSS probability1.88%
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 ATA 190 Series software allows remote attackers to disable the Ethernet interface with crafted ICMP traffic. The ICMP packet-processing path fails to rate-limit a steady stream of packets addressed to the device, forcing its Ethernet port offline. No authentication or user interaction is required; the web interface becomes unreachable and service remains interrupted until a manual power cycle.

The record

CVE
CVE-2021-34735
Published
Oct 6, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Analog Telephone Adaptor (ATA) Software
Classifications
CWE-770, T1498.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 6, 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 Analog Telephone Adaptor (ATA) Softwareversion=n/a

Published CVSS scores

8.6CiscoCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
7.5NIST NVDCVSS:3.1/AV:N/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.

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-770Allocation of Resources Without Limits or Throttling
T1498.001Network Denial of Service: Direct Network 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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