The developers of the Samba interoperability software suite announced on Wednesday the availability of security updates that patch a serious remote code execution vulnerability. Researchers have warned that there are many vulnerable systems accessible directly from the Internet.
The flaw, tracked as CVE-2017-7494, affects all versions of Samba since 3.5.0, released in March 2010. The security hole has been addressed in versions 4.6.4, 4.5.10 and 4.4.14, and a workaround has been made available for unsupported versions.
According to Samba maintainers, the vulnerability allows a malicious client to upload a shared library to a writable share, and cause the server to load and execute that file.
The vulnerability exposes various types of systems to attacks, including Linux and network-attached storage (NAS) devices. Rapid7 has warned that many users may not even realize that their systems are running Samba.
Samba provides file and print sharing capabilities between Windows and Unix computers, and it implements many protocols, including SMB, which malicious actors leveraged in the recent WannaCry ransomware attacks. This has led some experts to believe that CVE-2017-7494 could also be exploited for similar worm attacks.
“Unlike SMB, Samba exists on a wide variety of systems from different makers - servers, laptops, home routers, network storage systems, media servers, and many IoT devices. And unlike Windows, those devices may not automatically install an update - even if the manufacturer provides one,” researcher David Longenecker said in a blog post.
Exploiting the vulnerability is easy and proof-of-concept (PoC) code has already been made public, which could lead to in-the-wild attacks. HD Moore, VP of research and development at Atredis, has created a Metasploit module for CVE-2017-7494 and showed how the flaw can be exploited on Ubuntu and a Synology NAS product.
Re: Samba bug, the metasploit one-liner to trigger is just: simple.create_pipe("/path/to/target.so")
— HD Moore (@hdmoore) May 24, 2017
A scan conducted by Rapid7 with its Project Sonar showed more than 104,000 Internet-exposed endpoints running a vulnerable version of Samba, and nearly 90 percent of these systems had been running outdated versions of the software.
Individuals and organizations that still use older versions of Samba can prevent attacks by adding the parameter “nt pipe support = no” to the global section of their smb.conf file. RedHat also pointed out that the SELinux security module blocks potential exploits.
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