Actual Sync Server allows authenticated users to upload files through POST /sync/upload-user-file. In versions prior to 26.3.0, improper validation of the user-controlled x-actual-file-id header means that traversal segments (../) can escape the intended directory and write files outside userFiles.
The vulnerability can be mitigated in prior versions by running the sync server in a filesystem sandbox.
{
"github_reviewed": true,
"severity": "MODERATE",
"github_reviewed_at": "2026-03-10T01:02:15Z",
"cwe_ids": [
"CWE-22"
],
"nvd_published_at": "2026-03-09T14:16:10Z"
}