Updates released by Microsoft and Samba on Tuesday patch the vulnerability dubbed “Badlock,” although it turns out that the issue is not as severe as expected.
Samba is an open-source interoperability software suite that provides file and print services to SMB/CIFS clients. Stefan Metzmacher, an employee of SerNet and member of the Samba Core Team, discovered that the tool is plagued by a vulnerability that can be exploited for man-in-the-middle (MitM) and denial-of-service (DoS) attacks.
Roughly three weeks before the release of a patch, SerNet gave the vulnerability a name, Badlock, and created a website and a logo for it to raise awareness and to advertise its services.
Many experts criticized the company for the disclosure, arguing that it might have given malicious actors enough clues and enough time to come up with an exploit before a patch is released. However, it turns out that the issue is less severe than expected, and SerNet said the name assigned to the bug was meant to be generic instead of pointing to any specifics.
Microsoft, which classified the vulnerability as “important,” noted in its advisory that the issue affects the SAM and LSAD protocols.
“The vulnerability could allow elevation of privilege if an attacker launches a man-in-the-middle (MiTM) attack. An attacker could then force a downgrade of the authentication level of the SAM and LSAD channels and impersonate an authenticated user,” Microsoft said.
According to SerNet, Badlock can be exploited by an attacker with remote network connectivity to a targeted Samba service to launch DoS attacks. It also allows attackers to conduct MitM attacks against various protocols used by Samba, and execute arbitrary Samba network calls in the context of the intercepted user.
If they are able to intercept administrator network traffic, attackers can modify user permissions on files hosted on a standard Samba server, and view or modify secrets within an AD database (including user password hashes) on a Samba AD server.
SerNet expects that exploits for the vulnerability will be developed “pretty soon.” The company says it has several PoCs, but none of them will be released in the near future.
“Many attackers will use every tool in their toolbox to get into a network so there’s a good chance that Badlock will be used as a downstream vector,” Michael Gray, VP of Technology at Thrive Networks, told SecurityWeek. “For instance, an attacker can own a workstation via public Wi-Fi and then wait until that device is in a corporate environment. Once it detects a file server, it could inject payload into the server via Badlock or simply use it to download corporate data. It’s likely that Badlock could circumvent antivirus until all vendors have caught up, assuming, of course that a company’s antivirus is up to date and functional.”
Michael Gorelik, VP of R&D at Morphisec, believes that the hype created by SerNet took attention away from dozens of truly severe vulnerabilities that Microsoft patched on Tuesday.
“Unfortunately, Badlock is only an extreme example of a new trend,” Gorelik told SecurityWeek. “More and more companies use their findings for marketing reasons. This is not a problem if done responsibly, but SerNet exploited a real crisis that IT teams are facing. They simply cannot keep up with the sheer amount of patches – the gap is just getting bigger and bigger. Making the right choice about which patches to prioritize can be critical; being misled by those crying wolf can do real harm.”
Samba identifies the main flaw as CVE-2016-2118, while Microsoft tracks it as CVE-2016-0128. Additional CVEs assigned by Samba to Badlock are CVE-2015-5370, CVE-2016-2110, CVE-2016-2111, CVE-2016-2112, CVE-2016-2113, CVE-2016-2114 and CVE-2016-2115.
The vulnerability affects Samba versions 3.6.x, 4.0.x, 4.1.x, 4.2.0-4.2.9, 4.3.0-4.3.6, and 4.4.0, and it has been patched with the release of versions 4.2.10 / 4.2.11, 4.3.7 / 4.3.8, and 4.4.1 / 4.4.2. Microsoft fixed the issue in Windows with the security bulletin MS16-047.
In addition to MS16-047, Microsoft released 14 security bulletins as part of the March 2016 Patch Tuesday to fix tens of critical and important vulnerabilities affecting Windows, Internet Explorer, Edge, Office, .NET, and Adobe Flash Player. The company is not aware of any attacks exploiting these flaws.
*Updated with comment from Michael Gorelik
