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AUSCERT External Security Bulletin Redistribution
Advisory (icsa-21-313-06) OSIsoft PI Web API
10 November 2021
AusCERT Security Bulletin Summary
Product: OSIsoft PI Web API
Operating System: Windows
Impact/Access: Provide Misleading Information -- Existing Account
Access Confidential Data -- Existing Account
CVE Names: CVE-2021-3093
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ICS Advisory (ICSA-21-313-06)
OSIsoft PI Web API
Original release date: November 09, 2021
All information products included in https://us-cert.cisa.gov/ics are provided
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(DHS) does not provide any warranties of any kind regarding any information
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1. EXECUTIVE SUMMARY
o CVSS v3 6.9
o ATTENTION: Exploitable remotely/low attack complexity
o Vendor: OSIsoft
o Equipment: PI Web API
o Vulnerability: Cross-site Scripting
2. RISK EVALUATION
Successful exploitation of this vulnerability could allow a remote
authenticated attacker access to sensitive information or deliver false
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following versions of PI Web API, a data management platform, are affected:
o All versions of PI Web API 2019 SPI and prior
3.2 VULNERABILITY OVERVIEW
3.2.1 IMPROPER NEUTRALIZATION OF INPUT DURING WEB PAGE GENERATION ('CROSS-SITE
A remote authenticated attacker with write access to a PI Server could trick a
user into interacting with a PI Web API endpoint and redirect them to a
malicious website. As a result, a victim may disclose sensitive information to
the attacker or be provided with false information.
CVE-2021-3093 has been assigned to this vulnerability. A CVSS v3 base score of
6.9 has been calculated; the CVSS vector string is ( AV:N/AC:L/PR:H/UI:R/S:C/
o CRITICAL INFRASTRUCTURE SECTORS: Multiple Sectors
o COUNTRIES/AREAS DEPLOYED: Worldwide
o COMPANY HEADQUARTERS LOCATION: United States
OSIsoft reported this vulnerability to CISA.
OSIsoft recommends upgrading to PI Web API 2021. Additional information can be
found in the OSIsoft PI Web API security bulletin (registration required).
OSIsoft recommends applying the following workaround in PI Web API to help
reduce the risk:
Remove the OSIsoft.REST.Documentation.dll from the PI Web API installation
o The PI Web API installation directory is available at this registry entry:
o The default PI Web API installation directory is:
Removing this file will cause built-in documentation to no longer be
available. Navigating to the PI Web API endpoint with a browser will
result in an error; however, the PI Web API will continue to function
as a REST API
o Documentation can be found at the OSIsoft website . Alternately, users are
encouraged to limit access to PI Web API built-in documentation to
dedicated development environments
OSIsoft recommends users employ the following defense measures to lower the
impact of exploitation for PI Web API:
o Avoid adding authentication type "Anonymous" in PI Web API configuration
settings to limit exposure to authenticated users only,
o Consider using a web application firewall to block html responses from PI
Web API servers,
o Audit the AF hierarchy to ensure there are no unauthorized databases,
elements, or attributes,
o For Kerberos authentication configurations, use Group Policy to deny
network authentication to PI Server Administrator accounts on the PI Web
See the OSIsoft customer portal knowledge article for additional details and
associated security updates (registration required).
CISA reminds organizations to perform proper impact analysis and risk
assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices
on the ICS webpage on us-cert.cisa.gov . Several recommended practices are
available for reading and download, including Improving Industrial Control
Systems Cybersecurity with Defense-in-Depth Strategies .
Additional mitigation guidance and recommended practices are publicly available
on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper,
ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation
Organizations observing any suspected malicious activity should follow their
established internal procedures and report their findings to CISA for tracking
and correlation against other incidents.
CISA also recommends users take the following measures to protect themselves
from social engineering attacks:
o Do not click web links or open unsolicited attachments in email messages.
o Refer to Recognizing and Avoiding Email Scams for more information on
avoiding email scams.
o Refer to Avoiding Social Engineering and Phishing Attacks for more
information on social engineering attacks.
No known public exploits specifically target this vulnerability.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
CISA continuously strives to improve its products and services. You can help by
choosing one of the links below to provide feedback about this product.
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