Directory traversal vulnerability in the %m macro in the smb.conf configuration file in Samba before 2.2.0a allows remote attackers to overwrite certain files via a .. in a NETBIOS name, which is used as the name for a .log file.

The remote Samba server is be vulnerable to a remote file creation vulnerability. This vulnerability allows an attacker overwrite arbitrary files by supplying an arbitrartily formed NetBIOS machine name to this server, and to potentially become root on this host. 

Michal Zalewski discovered that Samba does not properly validate  NetBIOS names from remote machines.

By itself that is not a problem, except if Samba is configured to write log-files to a file that includes the NetBIOS name of the remote side by using the `%m' macro in the `log file' command. In that case an attacker could use a NetBIOS name like '../tmp/evil'. If the log-file was set to '/var/log/samba/%s' Samba would then write to /var/tmp/evil.

Since the NetBIOS name is limited to 15 characters and the `log file' command could have an extension to the filename the results of this are limited. However if the attacker is also able to create symbolic links on the Samba server they could trick Samba into appending any data they want to all files on the filesystem which Samba can write to.

The Debian GNU/Linux packaged version of Samba has a safe configuration and is not vulnerable.

As temporary workaround for systems that are vulnerable change all occurrences of the `%m' macro in smb.conf to `%l' and restart Samba.

Michal Zalewski has found a vulnerability in all versions of Samba prior to 2.0.10 where if a client sends an invalid netbios name Samba could be tricked into appending it's log to files writable by root.
This can be very dangerous if combined with a symlink created by a local user. Note that the log files must be specified as %m.log in order for this to work, and Mandrake Linux ships Samba by default using log.%m, thus it is not vulnerable 'out of the box'.

The remote Samba server, according to its version number, allows creation of arbitrary remote files. 

This vulnerability allows an attacker to overwrite arbitrary files by supplying an arbitrarily formed NetBIOS machine name to this server, and to potentially become root on the remote server. 

An attacker does not need any privileges to exploit this flaw.

ID	Name	Product	Family	Severity
1338	Samba < 2.0.10 Remote Arbitrary File Overwrite	Nessus Network Monitor	Samba	critical
14902	Debian DSA-065-1 : samba - remote file append/creation	Nessus	Debian Local Security Checks	critical
13877	Mandrake Linux Security Advisory : samba (MDKSA-2001:062)	Nessus	Mandriva Local Security Checks	critical
10786	Samba NETBIOS Name Traversal Arbitrary Remote File Creation	Nessus	Gain a shell remotely	critical

Detections

Analytics

CVE-2001-1162

high

Tenable Plugins

critical

critical

critical

critical