CVE-2021-30118: Kaseya VSA File Upload Vulnerability Exploitation (CVE-2021-30118)
The short version: An attacker can upload files with the privilege of the Web Server process for Kaseya VSA Unified Remote Monitoring & Management (RMM) 9.5.4.2149 and subsequently use these files to execute asp commands The api /SystemTab/uploader.aspx is vulnerable to an unauthenticated arbitrary file upload leading to RCE. This arbitrary file upload allows an attacker to place files of his own choosing on any location on the hard drive of the server the webserver process has access to, including (but not limited to) the webroot. If the attacker uploads files with code to the webroot (e.g. aspx code) he can then execute this code in the context of the webserver to breach either the integrity, confidentiality, or availability of the system or to steal credentials of other users. In other words, this can lead to a full system compromise. BreachRisk discovers exposed instances from your attack surface and flags this finding so you can prioritize by real-world breach risk.
At a glance
| Fact | Detail |
|---|---|
| Our severity take | High — BreachRisk score 6.9 (impact 4, likelihood 4) |
| CVSS v3.1 (NVD) | Unknown at time of writing |
| In CISA KEV? | Unknown at time of writing — check the KEV catalog |
| Known exploited? | Unknown at time of writing |
| Requires authenticated session? | Unknown at time of writing |
| CVE | CVE-2021-30118 |
What you need to know
Exposed Kaseya VSA Server appears vulnerable to exploitation of file upload vulnerability (CVE-2021-30118).
- How they find it — internet-facing exposure of the affected product is discoverable by routine scanning.
- How they use it — attackers exploit the vulnerability against reachable instances.
- What it leads to — compromise of the affected service and, depending on placement, a foothold for further movement.
How serious we see it
High — based on BreachRisk impact and likelihood scoring for this threat definition (score 6.9/9). Treat internet-facing instances as priority; confirm exposure and patch status before assuming you're clear.
Recommendations
- Apply security update to exposed Kaseya VSA Server.
- Restrict access to affected Kaseya instances to only trusted IP addresses.
How BreachRisk sees it
BreachRisk discovers internet-facing assets tied to this threat, fingerprints the product where possible, and flags exposure for CVE-2021-30118. Where authorized, it can go beyond detection with a bounded, non-disruptive check rather than leaving you with a maybe. Continuous outside-in coverage means the exposed service is already on your radar ranked by how it actually gets used against you.