Hackers can potentially exploit a format string vulnerability in remote wall requests in order to execute arbitrary code in Solaris, Sun Microsystems Inc.’s version of the Unix operating system, security experts have warned.
Sun Solaris versions 2.5.1, 2.6, 7, and 8 require a security patch to the utility rwall daemon or rpc.rwalld, the U.S.-government funded Computer Emergency Response Team/Coordination Center (CERT/CC) at Carnegie Mellon University in Pittsburgh said in an advisory May 1.
The rwall daemon listens for wall requests, which are used to send messages to terminals using a time-sharing system. CERT Advisory CA-2002-10 warns that it contains a format string vulnerability that could permit a hacker to get into the system by executing code with the privileges of the rwall daemon, usually root.
Sun Microsystems, headquartered in Palo Alto, Calif., has confirmed that there is a problem with rpc.rwalld and is currently working on a patch to fix the hole, according to CERT.
Disabling rpc.rwalld in “inetd.conf” is the recommended temporary security solution until patches are available, CERT said. Sun will release a security bulletin once the patches are available, CERT said.
By exhausting system resources, a hacker can cause the rwall daemon to generate an error message; the format string vulnerability is in the code which displays the error message. Though a hacker may potentially be able to consume system resources and prevent wall from executing either locally and remotely, in order to exploit the hole a combination of events must occur, CERT said. For example, it is difficult for remote users to control the system resources that they are attempting to exhaust in order to manipulate the system, CERT said.
The problem appears to be limited to Sun’s Solaris version of the Unix operating system, CERT said.
The CERT/CC advisory can be found at http://www.cert.org/advisories/CA-2002-10.html.