CVE-2021-30116

Unauthenticated credential leak and business logic flaw in Kaseya VSA <= v9.5.6

CRITICAL

9.8

CVSS Score

Published: July 9, 2021 at 12:00 AM UTC

Updated: August 14, 2026 at 05:36 AM UTC

2 products affected across 1 vendorVsa AgentVsa Server

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Severity

CRITICAL9.8

Exploitation

CISA KEV

Exploit prediction

EPSS 86%

SSVC

Active

Actively Exploited

CISA Known Exploited Vulnerabilities (KEV) Catalog

EPSS Score85.7%

EPSS (Exploit Prediction Scoring System) estimates a 85.7% chance this CVE is exploited in the wild within the next 30 days — higher than 100% of all CVEs. It complements CVSS: a high EPSS on a mid-severity CVE can still be urgent.

Kaseya Virtual System/Server Administrator (VSA) contains an information disclosure vulnerability allowing an attacker to obtain the sessionId that can be used to execute further attacks against the system.

Required Action

Apply updates per vendor instructions.

Ransomware Use

Known

Added to KEV

Nov 3, 2021

Remediation Due

Nov 17, 2021

1810 days overdue

Notes

https://nvd.nist.gov/vuln/detail/CVE-2021-30116

Description

Kaseya VSA before 9.5.7 allows credential disclosure, as exploited in the wild in July 2021. By default Kaseya VSA on premise offers a download page where the clients for the installation can be downloaded. The default URL for this page is https://x.x.x.x/dl.asp When an attacker download a client for Windows and installs it, the file KaseyaD.ini is generated (C:\Program Files (x86)\Kaseya\XXXXXXXXXX\KaseyaD.ini) which contains an Agent_Guid and AgentPassword This Agent_Guid and AgentPassword can be used to log in on dl.asp (https://x.x.x.x/dl.asp?un=840997037507813&pw=113cc622839a4077a84837485ced6b93e440bf66d44057713cb2f95e503a06d9) This request authenticates the client and returns a sessionId cookie that can be used in subsequent attacks to bypass authentication. Security issues discovered --- * Unauthenticated download page leaks credentials * Credentials of agent software can be used to obtain a sessionId (cookie) that can be used for services not intended for use by agents * dl.asp accepts credentials via a GET request * Access to KaseyaD.ini gives an attacker access to sufficient information to penetrate the Kaseya installation and its clients. Impact --- Via the page /dl.asp enough information can be obtained to give an attacker a sessionId that can be used to execute further (semi-authenticated) attacks against the system.