Remote unauthenticated attackers can overwrite arbitrary server files with attacker-controllable data. The data that the attacker can control is not entirely arbitrary. h2o writes a CSV/XLS/etc file to disk, so the attacker data is wrapped in quotations and starts with "C1", if they're exporting as CSV.
{
"github_reviewed": true,
"github_reviewed_at": "2023-12-15T03:12:43Z",
"nvd_published_at": "2023-12-14T13:15:55Z",
"cwe_ids": [
"CWE-610",
"CWE-73"
],
"severity": "CRITICAL"
}