CVE-2021-33436

SYSTEM code execution via unsafe DLL search

Published Apr 28, 2022 · Updated Aug 3, 2024

DLL search-order hijacking in NoMachine Server 6 before 6.15.1 and 7 before 7.5.2 allows local users to execute code as SYSTEM. The server uses the Windows DLL search order without excluding nonadministrator-writable directories listed in the system PATH. Exploitation requires such a directory in PATH, after which a planted library runs as NT AUTHORITY\SYSTEM.

CVSS severity7.3
High
EPSS probability0.28%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DLL search-order hijacking in NoMachine Server 6 before 6.15.1 and 7 before 7.5.2 allows local users to execute code as SYSTEM. The server uses the Windows DLL search order without excluding nonadministrator-writable directories listed in the system PATH. Exploitation requires such a directory in PATH, after which a planted library runs as NT AUTHORITY\SYSTEM.

The record

CVE
CVE-2021-33436
Published
Apr 28, 2022
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1574.001
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 28, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.3NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
6.2NIST NVDAV:L/AC:H/Au:N/C:C/I:C/A:C

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1574.001Hijack Execution Flow: DLL Search Order Hijacking

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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