6.8 Medium
CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:M/Au:N/C:P/I:P/A:P
8.1 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
8.2 High
AI Score
Confidence
High
0.1 Low
EPSS
Percentile
94.9%
This updated advisory is a follow-up to the original advisory titled ICSA-22-132-13 Siemens Industrial Devices using libcurl (Update A) that was published June 16, 2022, on the ICS webpage on cisa.gov/ics.
Successful exploitation of these vulnerabilities could crash and allow an attacker to interfere with the affected products in various ways.
Siemens reports these vulnerabilities affect the following Siemens Industrial Devices using libcurl:
--------- Begin Update B Part 1 of 2 ---------
--------- End Update B Part 1 of 2 ---------
libcurl 7.75.0 through 7.76.1 suffers from a use-after-free vulnerability resulting in already freed memory being used when a TLS 1.3 session ticket arrives over a connection. A malicious attacker can use this to reach remote code execution in the client.
When libcurl at run-time sets up support for TLS 1.3 session tickets on a connection using OpenSSL, it stores pointers to the transfer in-memory object for later retrieval when a session ticket arrives. If the connection is used by multiple transfers (as with a reused HTTP/1.1 connection or multiplexed HTTP/2 connection) that first transfer object might be freed before the new session is established and the function will then access a memory buffer that might be freed. When using that memory, libcurl may call a function pointer in the object, making it possible for remote code execution if the server could manage to get crafted memory content into the correct place in memory.
CVE-2021-22901 has been assigned to this vulnerability. A CVSS v3 base score of 8.1 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).
libcurl keeps previously used connections in a connection pool for subsequent transfers to reuse if one of them matches the setup. Due to errors in the logic, the config matching function did not take ‘issuercert’ into account and compares the involved paths case insensitively, which could lead to libcurl reusing wrong connections. File paths are, or can be, case sensitive on many systems and can vary depending on used file systems. The comparison also didn’t include the ‘issuer cert,’ which a transfer can set to qualify how to verify the server certificate.
CVE-2021-22924 has been assigned to this vulnerability. A CVSS v3 base score of 3.7 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N).
Siemens notified CISA these devices are affected by these known vulnerabilities.
Siemens has released updates for several affected products and recommends updating to the latest versions. Siemens is preparing further updates and recommends countermeasures for products where updates are not yet available.
--------- Begin Update B Part 2 of 2 ---------
--------- End Update B Part 2 of 2 ---------
As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. To operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens’ operational guidelines for industrial security and to follow the recommendations in the product manuals.
Additional information on industrial security by Siemens can be found on the Siemens industrial security webpage.
For additional information, please refer to Siemens Security Advisory SSA-732250
CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should:
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 cisa.gov/ics. 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 cisa.gov/ics in the Technical Information Paper, ICS-TIP-12-146-01B–Targeted Cyber Intrusion Detection and Mitigation Strategies.
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.
No known public exploits specifically target these vulnerabilities. These vulnerabilities have a high attack complexity.
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-22901
web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-22924
cert-portal.siemens.com/operational-guidelines-industrial-security.pdf
cert-portal.siemens.com/productcert/pdf/ssa-732250.pdf
cisa.gov/ics
cisa.gov/ics
cwe.mitre.org/data/definitions/416.html
cwe.mitre.org/data/definitions/416.html
public.govdelivery.com/accounts/USDHSCISA/subscriber/new?topic_id=USDHSCISA_138
support.industry.siemens.com/cs/ww/en/view/109807276
support.industry.siemens.com/cs/ww/en/view/109808678
support.industry.siemens.com/cs/ww/en/view/109810215
support.industry.siemens.com/cs/ww/en/view/109811169/
support.industry.siemens.com/cs/ww/en/view/109812218
twitter.com/CISAgov
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www.cisa.gov/uscert/ics/alerts/ICS-ALERT-10-301-01
www.cisa.gov/uscert/ics/recommended-practices
www.cisa.gov/uscert/ics/tips/ICS-TIP-12-146-01B
www.cisa.gov/uscert/sites/default/files/recommended_practices/NCCIC_ICS-CERT_Defense_in_Depth_2016_S508C.pdf
www.dhs.gov
www.dhs.gov/foia
www.dhs.gov/performance-financial-reports
www.facebook.com/CISA
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www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:O/RC:C
www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N/E:P/RL:O/RC:C
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mailto:?subject=Siemens%20Industrial%20Devices%20using%20libcurl%20%28Update%20B%29&body=www.cisa.gov/news-events/ics-advisories/icsa-22-132-13
6.8 Medium
CVSS2
Attack Vector
NETWORK
Attack Complexity
MEDIUM
Authentication
NONE
Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
AV:N/AC:M/Au:N/C:P/I:P/A:P
8.1 High
CVSS3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
8.2 High
AI Score
Confidence
High
0.1 Low
EPSS
Percentile
94.9%