Successful exploitation of this vulnerability could allow an attacker to hijack existing sessions or spoof future sessions.
The following products from Siemens are affected:
Initial sequence numbers (ISNs) for TCP connections are derived from an insufficiently random source; the ISN of current and future TCP connections could be predictable. An attacker could hijack existing sessions or spoof future sessions.
CVE-2020-28388 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated. the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L)
Siemens reported these vulnerabilities to CISA.
Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:
As a general security measure, Siemens strongly recommends protecting network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemensβ operational guidelines for industrial security and to follow the recommendations in the product manuals.
For more information, see the associated Siemens security advisory SSA-408105 in HTML and CSAF.
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. 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 at cisa.gov/ics. Several CISA products detailing cyber defense best 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 at cisa.gov/ics in the technical information paper, ICS-TIP-12-146-01BβTargeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.
No known public exploits specifically target this vulnerability.
cert-portal.siemens.com/productcert/csaf/ssa-408105.json
cert-portal.siemens.com/productcert/html/ssa-408105.html
cisa.gov/ics
cisa.gov/ics
cwe.mitre.org/data/definitions/342.html
nvd.nist.gov/vuln/detail/CVE-2020-28388
partnerportal.extranet.dc.siemens.com/
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