Microsoft accidentally leaks details on a wormable SMB flaw

No patch is currently available for the vulnerability, which has now been publicly acknowledged

Microsoft accidentally released information on a critical flaw embedded in its Server Message Block 3.0 (SMBv3) network communications protocol ahead of schedule, coinciding with more than a hundred Patch Tuesday fixes.

Details of the wormable vulnerability, which has been reserved CVE-220-0796, were disclosed publicly shortly after Microsoft prematurely informed security vendors of the bug through its Active Protections Program scheme. This early-access information, however, was retracted shortly after.

Attackers can exploit the remote code execution vulnerability found in SMBv3 by sending a specially-crafted packet to the targeted SMBv3 server - to which the hacker must already be connected to. 

Advertisement - Article continues below

Vulnerable operating systems include Windows 10 1903 and 1909 for 32-bit, x64-bit and ARM64-based systems, as well as Windows Server versions 1903 and 1909.

Security firm Fortinet has suggested the vulnerability is due to an error when the software handles any maliciously crafted data packet, which can lead to hackers gaining full control of a vulnerable system. It’s considered ‘wormable’ as it's believed an attacker could easily move from device to device.

Both Fortinet and Cisco Talos have recommended that users disable SMBv3 compression and block TCP port 445 on firewalls and client computers.

After the details became public, Microsoft released its own security advisory suggesting the company was aware of the flaw, although official mitigation has not yet been identified.

Advertisement - Article continues below

“To exploit the vulnerability against an SMB Server, an unauthenticated attacker could send a specially crafted packet to a targeted SMBv3 Server,” the advisory said.

“To exploit the vulnerability against an SMB Client, an unauthenticated attacker would need to configure a malicious SMBv3 Server and convince a user to connect to it.”

Related Resource

Three keys to maximise application migration and modernisation success

Harness the benefits that modernised applications can offer

Download now

Microsoft confirmed a workaround that involves disabling SMBv3 compression using a PowerShell command may be deployed, although the firm added this does not prevent exploitation of SMB clients.

Details of the vulnerability were made public just as Microsoft released fixes for 117 flaws in various systems, including 25 vulnerabilities considered critical, as part of its routine Patch Tuesday round of fixes.

Featured Resources

The case for a marketing content hub

Transform your digital marketing to deliver customer expectations

Download now

Fast, flexible and compliant e-signatures for global businesses

Be at the forefront of digital transformation with electronic signatures

Download now

Why CEOS should care about the move to SAP S/4HANA

And how they can accelerate business value

Download now

IT faces new security challenges in the wake of COVID-19

Beat the crisis by learning how to secure your network

Download now


operating systems

How to factory reset Windows 10

4 Mar 2020
artificial intelligence (AI)

Can Microsoft's new approach to AI erase the memory of Tay?

30 May 2020

Linux GUI apps coming to Windows 10

22 May 2020

The IT Pro Podcast: Microsoft Build goes virtual

22 May 2020

Most Popular


Ransomware collective claims to have hacked NASA IT contractor

3 Jun 2020

The UK looks to Japan and South Korea for 5G equipment

4 Jun 2020

How data science is transforming business

29 May 2020