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Siemens on Friday shipped firmware updates to address a severe vulnerability in SIMATIC S7-1200 and S7-1500 programmable logic controllers (PLCs) that could be exploited by a malicious actor to remotely gain access to protected areas of the memory and achieve unrestricted and undetected code execution, in what the researchers describe as an attacker’s “holy grail.”

The memory protection bypass vulnerability, tracked as CVE-2020-15782 (CVSS score: 8.1), was discovered by operational technology security company Claroty by reverse-engineering the MC7 / MC7+ bytecode language used to execute PLC programs in the microprocessor. There’s no evidence that the weakness was abused in the wild.

In an advisory issued by Siemens, the German industrial automation firm said an unauthenticated, remote attacker with network access to TCP port 102 could potentially write arbitrary data and code to protected memory areas or read sensitive data to launch further attacks.

“Achieving native code execution on an industrial control system such as a programmable logic controller is an end-goal relatively few advanced attackers have achieved,” Claroty researcher Tal Keren said. “These complex systems have numerous in-memory protections that would have to be hurdled in order for an attacker to not only run code of their choice, but also remain undetected.”

 

images from Hacker News