CVE-2020-9451

An issue was discovered in Acronis True Image 2020 24.5.22510. anti_ransomware_service.exe keeps a log in a folder where unprivileged users have write permissions. The logs are generated in a predictable pattern, allowing an unprivileged user to create a hardlink from a (not yet created) log file to anti_ransomware_service.exe. On reboot, this forces the anti_ransomware_service to try to write its log into its own process, crashing in a SHARING VIOLATION. This crash occurs on every reboot.

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://danishcyberdefence.dk/blog
• https://madsjoensen.dk/cve-2020-9451/
• https://www.acronis.com