Prepare to patch a critical flaw in Windows and Samba file sharing in 3 weeks

The Badlock vulnerability is severe and likely to be exploited soon after disclosure

Systems administrators should get ready to fix a critical vulnerability on April 12 that affects the Windows and Samba implementations of the Server Message Block (SMB) protocol.

The vulnerability was discovered by Stefan Metzmacher, a core developer of the Samba software, which is a popular open-source implementation of the SMB/CIFS (Server Message Block/Common Internet File System) networking protocol.

SMB/CIFS is implemented by default in Windows, where it's used for network file and printer sharing. Linux and other Unix-like systems can interoperate and share resources with Windows systems over the same protocol using the Samba software.

"On April 12th, 2016, SerNet, the Samba Team and Microsoft will disclose a severe bug that affects almost all versions of Microsoft Windows and Samba," said SerNet, the company where Metzmacher works, in an announcement on its website. "The bug is called 'Badlock'."

The company, which offers Samba consulting, support and development services, has even set up an website at where more details will be released about the flaw on the disclosure date, which coincides with Microsoft's Patch Tuesday -- the day when Microsoft releases its monthly security updates.

"Please get yourself ready to patch all systems on this day," a warning on the website reads. "We are pretty sure that there will be exploits soon after we publish all relevant information."

There's been a bit of speculation on Twitter from members of the security community about where the flaw might be. The name itself seems to suggest that it's related to the client lock-handling mechanism, and there's actually file in the Samba source code called lock.c that has a copyright  by Stefan Metzmacher.

Because the vulnerability affects both Samba and Windows, which are separate implementations of the protocol, there's a good chance that it's actually a protocol design flaw.

"With both vendors apparently offering patches, it suggests the vulnerability is either within the integration between the two vendors, the separate implementations by each vendor, or in the SMB/CIFS protocol itself (we’re betting on the latter)," said Brian Martin, director of vulnerability intelligence at security firm Risk Based Security, in a blog post.

As far as the impact of the vulnerability goes, Johannes Loxen, the CEO of SerNet, said on Twitter that "#badlock means admin accounts for everyone on the same LAN." The message appears to have since been deleted, but a CSO article on the controversy over SerNet's use of the flaw for marketing purposes includes a screenshot of it.

The disclosure of the bug's existence, even without specific technical details, three weeks in advance has also been criticized by some members of the security community because it gives potential hackers ample time to find it on their own.

"Odds on the details of Badlock leaking (or being independently discovered) before April 12th? 15/1," said renowned security researcher David Litchfield in a Twitter message.

Join the CSO newsletter!

Error: Please check your email address.

More about CSOLANLinuxMicrosoftTwitter

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Lucian Constantin

Latest Videos

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts