An issue was discovered in Acronis True Image 2020 24.5.22510. antiransomwareservice.exe includes functionality to quarantine files by copying a suspected ransomware file from one directory to another using SYSTEM privileges. Because unprivileged users have write permissions in the quarantine folder, it is possible to control this privileged write with a hardlink. This means that an unprivileged user can write/overwrite arbitrary files in arbitrary folders. Escalating privileges to SYSTEM is trivial with arbitrary writes. While the quarantine feature is not enabled by default, it can be forced to copy the file to the quarantine by communicating with antiransomwareservice.exe through its REST API.

An issue was discovered in Acronis True Image 2020 24.5.22510. antiransomwareservice.exe exposes a REST API that can be used by everyone, even unprivileged users. This API is used to communicate from the GUI to antiransomwareservice.exe. This can be exploited to add an arbitrary malicious executable to the whitelist, or even exclude an entire drive from being monitored by antiransomwareservice.exe.

An issue was discovered in Acronis True Image 2020 24.5.22510. antiransomwareservice.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 antiransomwareservice.exe. On reboot, this forces the antiransomwareservice to try to write its log into its own process, crashing in a SHARING VIOLATION. This crash occurs on every reboot.