CVE-2021-27576Network attack vector

Bandwidth exhaustion via unrestricted NetTest requests

Published Mar 15, 2021 · Updated Feb 13, 2025

Uncontrolled resource consumption in Apache OpenMeetings 4.0.0 through 5.1.0 allows remote attackers to exhaust server bandwidth. The public NetTestWebService accepts attacker-selected transfer sizes and streams generated bytes without effective size and concurrent-client limits. No authentication or user interaction is required, and repeated requests can consume network capacity and interrupt service availability.

CVSS severity7.5
High
EPSS probability2.84%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Apache OpenMeetings 4.0.0 through 5.1.0 allows remote attackers to exhaust server bandwidth. The public NetTestWebService accepts attacker-selected transfer sizes and streams generated bytes without effective size and concurrent-client limits. No authentication or user interaction is required, and repeated requests can consume network capacity and interrupt service availability.

The record

CVE
CVE-2021-27576
Published
Mar 15, 2021
Updated
Feb 13, 2025
Vendor
The Apache Software Foundation
Product
Apache OpenMeetings
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 2025Record 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=4.0.0 <Apache OpenMeetings 4*
  2. Affected versionversion=Apache OpenMeetings 5 <=5.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache OpenMeetingsversion=4.0.0 <Apache OpenMeetings 4*; version=Apache OpenMeetings 5 <=5.1.0

Published CVSS scores

7.5GitHub Security AdvisoryCVSS: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.

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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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
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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