Executive Summary

[{'type': 'paragraph', 'content': "CVE-2016-20025 is a privilege escalation vulnerability in ZKTeco ZKAccess Professional version 3.5.3. The issue arises because the software improperly assigns 'Modify' permissions to the 'Authenticated Users' group on its executable files. This means that any user who is authenticated on the system can replace the legitimate executable binaries with malicious code."}, {'type': 'paragraph', 'content': 'By exploiting this insecure file permission setting, an attacker can escalate their privileges locally by running malicious code with higher privileges than they should have.'}] [1, 2, 3, 4]

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Impact Analysis

This vulnerability allows any authenticated user on the affected system to escalate their privileges by replacing executable files with malicious binaries. As a result, an attacker could gain higher-level access than intended, potentially compromising the security of the system.

Such privilege escalation can lead to unauthorized access to sensitive data, modification of system settings, installation of persistent malware, or disruption of normal system operations.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'This vulnerability can be detected by checking the file permissions of the executable file "ZKAccess3.5" on the affected system. Specifically, you need to verify if the "Authenticated Users" group has the "Modify" (M) permission on this executable, which should not be the case.'}, {'type': 'paragraph', 'content': 'On Microsoft Windows systems, you can use the following command to check the permissions:'}, {'type': 'list_item', 'content': 'icacls ZKAccess3.5'}, {'type': 'paragraph', 'content': 'If the output shows that "Authenticated Users" have modify rights (including inheritance flags such as OI, CI, IO), this indicates the presence of the vulnerability.'}] [2, 3]

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Mitigation Strategies

[{'type': 'paragraph', 'content': 'To mitigate this vulnerability immediately, you should remove or restrict the "Modify" permission granted to the "Authenticated Users" group on the executable files of ZKTeco ZKAccess Professional 3.5.3.'}, {'type': 'paragraph', 'content': 'This can be done by adjusting the file permissions to ensure that only trusted administrative users have modify or write access to the executable files, preventing authenticated but unprivileged users from replacing the binaries with malicious code.'}, {'type': 'paragraph', 'content': 'Using Windows, you can modify the permissions with the icacls command, for example:'}, {'type': 'list_item', 'content': 'icacls ZKAccess3.5 /remove:g "Authenticated Users"'}, {'type': 'paragraph', 'content': 'Alternatively, explicitly deny modify permissions or set more restrictive ACLs to prevent unauthorized modification.'}, {'type': 'paragraph', 'content': 'Additionally, ensure that only trusted users have authenticated access to the system and consider applying any available patches or updates from the vendor.'}] [2, 3, 4]

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