CVE-2021-30201: Kaseya VSA XML External Entity Reference ('XXE') Vulnerability Exploitation (CVE-2021-30201)
The short version: The API endpoint /vsaWS/KaseyaWS.asmx can be used to submit XML to the system. When this XML is processed (external) entities are insecurely processed and fetched by the system and returned to the attacker. Using this vulnerability an attacker can read any file on the server the webserver process can read. Additionally, it can be used to perform HTTP(s) requests into the local network and thus use the Kaseya system to pivot into the local network. 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 6.0 (impact 4, likelihood 3) |
| 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-2021-30201 |
What you need to know
Exposed Kaseya VSA Server appears vulnerable to exploitation of xml external entity reference ('xxe') vulnerability (CVE-2021-30201).
- 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 6.0/9). 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-2021-30201. 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.