CVE-2021-30121: Kaseya VSA LFI Vulnerability Exploitation (CVE-2021-30121)
The short version: Semi-authenticated local file inclusion The contents of arbitrary files can be returned by the webserver Example request: https://x.x.x.x/KLC/js/Kaseya.SB.JS/js.aspx?path=C:\Kaseya\WebPages\dl.asp A valid sessionId is required but can be easily obtained via CVE-2021-30118. 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 | Moderate — BreachRisk score 5.3 (impact 2, 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-2021-30121 |
What you need to know
Exposed Kaseya VSA Server appears vulnerable to exploitation of file upload vulnerability (CVE-2021-30121).
- 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
Moderate — based on BreachRisk impact and likelihood scoring for this threat definition (score 5.3/9). 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-2021-30121. 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.