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Samba Security Advisory: Root Access Risk Fix and Interim Mitigation

A serious security hole has been discovered in all versions of Samba that allows an attacker to gain root access on the target machine for certain types of common Samba configuration. Until all vendors have released updates, there is an interim workaround available. . . .. A serious security hole has been discovered in all versions of Samba that allows an attacker to gain root access on the target machine for certain types of common Samba configuration. Until all vendors have released updates, there is an interim workaround available. IMPORTANT: Security bugfix for Samba ------------------------------------ June 23rd 2001 Summary ------- A serious security hole has been discovered in all versions of Samba that allows an attacker to gain root access on the target machine for certain types of common Samba configuration. The immediate fix is to edit your smb.conf configuration file and remove all occurances of the macro "%m". Replacing occurances of %m with %I is probably the best solution for most sites. Details ------- A remote attacker can use a netbios name containing unix path characters which will then be substituted into the %m macro wherever it occurs in smb.conf. This can be used to cause Samba to create a log file on top of an important system file, which in turn can be used to compromise security on the server. The most commonly used configuration option that can be vulnerable to this attack is the "log file" option. The default value for this option is VARDIR/log.smbd. If the default is used then Samba is not vulnerable to this attack. The security hole occurs when a log file option like the following is used: log file = /var/log/samba/%m.log In that case the attacker can use a locally created symbolic link to overwrite any file on the system. This requires local access to the server. If your Samba configuration has something like the following: log file = /var/log/samba/%m Then the attacker could successfully compromise your server remotely as no symbolic linkis required. This type of configuration is very rare. The most commonly used log file configuration containing %m is the distributed in the sample configuration file that comes with Samba: log file = /var/log/samba/log.%m in that case your machine is not vulnerable to this attack unless you happen to have a subdirectory in /var/log/samba/ which starts with the prefix "log." New Release ----------- While we recommend that vulnerable sites immediately change their smb.conf configuration file to prevent the attack we will also be making new releases of Samba within the next 24 hours to properly fix the problem. Please see for the new releases. Please report any attacks to the appropriate authority. The Samba Team This email address is being protected from spambots. You need JavaScript enabled to view it. . A critical vulnerability in OpenSSH grants malicious users elevated privileges, with temporary remediation guidelines outlined.. Samba Security, Root Access Risk, Samba Configuration, Security Bugfix. . LinuxSecurity.com Team

Jun 23, 2001 • LinuxSecurity.com Team Server Security