On March 10, Security Advisory ADV200005 was released with Patch Tuesday updates that revealed details on a remote code execution vulnerability in the way Server Message Block 3.1.1 (SMBv3) handles connections that use compression. Despite March patch Tuesday marking the largest Patch Tuesday ever, with a whopping 115 CVEs resolved, CVE-2020-0796 created a lot of fuss among the security communities.
As stated in ADV200005, “To exploit CVE-2020-0796 against an SMB Server, an unauthenticated attacker could send a specially crafted packet to a targeted SMBv3 Server. To exploit an SMB Client, an unauthenticated attacker would need to configure a malicious SMBv3 Server and convince a user to connect to it.”
The wormable nature of CVE-2020-0796 is reminiscent of EternalBlue, a remote code execution (RCE) vulnerability in SMBv1, which was the prime vector of the disastrous WannaCry. This comparison has created so much fear that it could be weaponized to launch a new wave of WannaCry and NotPetya, that researchers are even referring to it as EternalDarkness, along the lines of EternalBlue.
A day before the patch was released, cybersecurity firm Kryptos Logic shared on Twitter a basic denial-of-service proof-of-concept (PoC) exploit demo leveraging CVE-2020-0796. Kryptos Logic also announced that it identified around 48,000 vulnerable hosts across the internet that had the SMB port exposed and these hosts were likely to fall victim to potential attacks using EternalDarkness. Since PoC exploits have already been developed, it’s high time that you’ve pushed KB4551762 to your vulnerable systems.
If you have difficulty applying the applying KB4551762, Microsoft recommends mitigation measures for SMB servers in it’s security advisory.
Tackling EternalDarkness and other critical vulnerabilities are a piece of cake with our prioritization-driven threat and vulnerability management solution, Vulnerability Manager Plus. Vulnerability Manager Plus empowers you with a dedicated “zero-day vulnerabilities” tab to give you targeted visibility over any zero-day vulnerabilities, as well as publicly disclosed and other critical vulnerabilities that could be exploited easily. From this module, you can easily fix CVE-2020-0796 since patches are automatically correlated beforehand. Furthermore, it enables you to test the updates in a pilot group before rolling them rolling them out to your production machines. And, it’s imperative that you perform patch testing, especially since out-of-band updates have resulted in issues in the past. With a robust security configuration feature baked into Vulnerability Manager Plus, you can even block TCP port 445 in the affected endpoints since that is the best defense against SMB-related wormable attacks.
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