cbcvebase.
CVE-2021-30116
published 2021-07-09

CVE-2021-30116: 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…

PriorityP196critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
KEVITWEXPLOITRansomware
CISA Known Exploited Vulnerabilitydue 2021-11-17
Exploited in the wild
EPSS
85.62%
99.7th percentile
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.

Affected

3 ranges
VendorProductVersion rangeFixed in
kaseyavsa< 9.5.69.5.6
kaseyavsa_agent< 9.5.0.249.5.0.24
kaseyavsa_server< 9.5.7a9.5.7a

Detection & IOCsextracted from sources · hover to see the quote

url/InstallTab/exportFldr.asp?fldrId=%28SELECT%20%28CASE%20WHEN%20%281%3D1%29%20THEN%201%20ELSE%20%28SELECT%201%20UNION%20SELECT%202%29%20END%29%29
cookiesessionId=30548861; agentguid=840997037507813; vsaUser=scopeId=3&roleId=2
url/userFilterTableRpt.asp
  • Detect boolean-based blind SQL injection attempts against /InstallTab/exportFldr.asp via the fldrId parameter — a 500 response to a trailing single-quote and a 200 response to a CASE/WHEN payload is the distinguishing pattern.
  • Alert on the creation of cert.exe in C:\Windows\ — this is certutil.exe copied and renamed to evade detection before decoding the ransomware payload.
  • Detect PowerShell invocations that set Set-MpPreference with -DisableRealtimeMonitoring $true alongside multiple other Defender-disabling flags in a single command line.
  • Monitor for IIS log deletion and application database log deletion as an early-stage indicator of the REvil VSA attack chain.
  • ·The SQL injection exploit requires a semi-authenticated session — the sessionId cookie value must first be obtained via CVE-2021-30116 (credential leak). Detections relying solely on unauthenticated traffic may miss this attack chain.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.07.5HIGHAV:N/AC:L/Au:N/C:P/I:P/A:P
vulncheck10.0CRITICAL
cisa9.8CRITICAL
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