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Advisory: Dual DHCP DNS Server V7.40 Privilege Escalation (CVE-2020-26133)

Summary

Product: Dual DHCP DNS Server
Affected version: V7.40
Vendor: Achal Dhir
Fixed version: No response from vendor
Tested version: V7.40
CVE Reference: CVE-2020-26133
CWE Reference: CWE-269

Problem Description

The folder permissions on the default installation directory %SYSTEMDRIVE%\DualServer\ allows anyone in the "Authenticated Users" group to modify its contents. To exploit this vulnerability, a local attacker can replace the DualServer.exe with a crafted binary with the same name. Afterwards, if the service is restarted, the attacker's code will be executed in the context of system. The service gets automatically started after a reboot.

Impact

By replacing the binary an attacker can execute code, allowing potential privilege escalation to system.

Workaround

It is advised to change the installation directory to %SYSTEMDRIVE%\Program Files\ or %SYSTEMDRIVE%\Program Files(x86)\. By default, these directories allow "Authenticated Users" to only read and execute the directory contents.

Notes

The issue was reported to the vendor, but there was no response.

Disclosure Timeline

2020-07-28: Vulnerability discovered
2020-07-28: Vulnerability reported to vendor via Sourceforge
2020-09-29: CVE reserved
2020-10-26: 90-day disclosure deadline passed
2020-10-28: Published advisory

References

https://sourceforge.net/projects/dhcp-dns-server/

Changes

2020-11-30: Corrected CWE

EOF