CVE-2021-33527Network attack vector

Unauthenticated SYSTEM code execution via unvalidated HTTP request

Published Aug 2, 2021 · Updated Sep 16, 2024

OS command injection in MB connect line mbDIALUP 3.9R0.0 and earlier allows remote attackers to execute code as SYSTEM via HTTP. The mbConnect24serv service runs as NT AUTHORITY\SYSTEM and accepts a crafted HTTP request without correctly validating its input before directing code execution. No authentication or user interaction is required, and successful exploitation grants full service privileges on the Windows host.

CVSS severity9.8
Critical
EPSS probability4.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OS command injection in MB connect line mbDIALUP 3.9R0.0 and earlier allows remote attackers to execute code as SYSTEM via HTTP. The mbConnect24serv service runs as NT AUTHORITY\SYSTEM and accepts a crafted HTTP request without correctly validating its input before directing code execution. No authentication or user interaction is required, and successful exploitation grants full service privileges on the Windows host.

The record

CVE
CVE-2021-33527
Published
Aug 2, 2021
Updated
Sep 16, 2024
Vendor
MB connect line
Product
mbDIALUP
Classifications
CWE-20, CWE-78, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 2, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=3.9R0.0 <=3.9R0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MB connect line · mbDIALUPversion=3.9R0.0 <=3.9R0.0

Published CVSS scores

9.8CERT@VDECVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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-78Improper Neutralization of Special Elements used in an OS Command
T1190Exploit Public-Facing Application

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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