CVE-2021-40122Network attack vector

Unauthenticated reload via oversized message series

Published Oct 21, 2021 · Updated Nov 7, 2024

A denial-of-service vulnerability in Cisco Meeting Server allows unauthenticated remote attackers to reload the device via the Call Bridge API. The API improperly handles a large series of message requests, and sustained requests trigger a reload that drops all ongoing calls. The attack requires network reachability to the vulnerable API but no authentication or user interaction; impact is service interruption without reported confidentiality or integrity loss.

CVSS severity5.9
Medium
EPSS probability1.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A denial-of-service vulnerability in Cisco Meeting Server allows unauthenticated remote attackers to reload the device via the Call Bridge API. The API improperly handles a large series of message requests, and sustained requests trigger a reload that drops all ongoing calls. The attack requires network reachability to the vulnerable API but no authentication or user interaction; impact is service interruption without reported confidentiality or integrity loss.

The record

CVE
CVE-2021-40122
Published
Oct 21, 2021
Updated
Nov 7, 2024
Vendor
ClamAV
Product
Cisco Meeting Server
Classifications
CWE-404, CWE-399, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 21, 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 Meeting Serverversion=n/a

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.9Cisco Systems, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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-404Improper Resource Shutdown or Release
CWE-399Resource Management Errors
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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