The bufprint routine used by capi_cmsg2str does an unbounded vsprintf into a 8192 byte buffer, perhaps hoping it's big enough. If the content of that vsprintf can be controlled by remote peers, this may lead to a remote security hole for daemons using CAPI (pppd-capi-plugin, asterisk-chan-capi, capi4hylafax, ...). Or a DoS. If the content of that vsprintf can be controlled by local users making use of a system service (such as sending a fax, making a phone call, ...) that uses CAPI, this is a privilege escalation or remote authenticated user security hole, or a DoS.
Marcel, the exploit in bug 230563 comment #1 requires access to /dev/capi20, which has permission 600 (and thus needs super-user privileges). If that is our only exposure, please close this as NOTABUG.
Created attachment 150897 [details] patch for this BZ
Created attachment 150899 [details] CVS repository patch, adds CONFIG_CAPI_TRACE option
Compilation is successful but not tested, because i do not have ISDN card available.
Patch still contains errors, please do not test it now.
Created attachment 151273 [details] correct patch, only compilation tested, need to test with real hardware
fixed in build 2.4.21-51.EL
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on the solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2007-0671.html
*** Bug 402771 has been marked as a duplicate of this bug. ***