CVE-2020-15843

ActFax Version 7.10 Build 0335 (2020-05-25) is susceptible to a privilege escalation vulnerability due to insecure folder permissions on %PROGRAMFILES%ActiveFaxClient, %PROGRAMFILES%ActiveFaxInstall and %PROGRAMFILES%ActiveFaxTerminal. The folder permissions allow Full Control to Everyone. An authenticated local attacker can exploit this to replace the TSClientB.exe binary in the Terminal directory, which is executed on logon for every user. Alternatively, the attacker can replace any of the binaries in the Client or Install directories. The latter requires additional user interaction, for example starting the client.

Weakness

During installation, installed file permissions are set to allow anyone to modify those files.

Affected Software

Potential Mitigations

• Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
• Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/1.html
• https://cwe.mitre.org/data/definitions/127.html
• https://cwe.mitre.org/data/definitions/81.html

References

• https://blog.to.com/advisory-actfax-7-10-build-0335-privilege-escalation-cve-2020-15843/