Check Point Software Technologies - Vulnerability Discovery Team (VDT) http://www.checkpoint.com/defense/ rpc.pcnfsd syslog format string vulnerability CVE-2010-1039 INTRODUCTION There exists a vulnerability within a log function of the rpc.pcnfsd service which when properly exploited can lead to remote compromise of the vulnerable system. This vulnerability was confirmed in the following versions and operating systems, other versions and operating systems may be also affected. IBM AIX 6.1.0 and lower IRIX 6.5 HP-UX 11.11, 11.23, 11.31 DETAILS This vulnerability can be triggered by sending a rpc request resulting in an invalid directory causing the service to call _msgout() function that call syslog() function to log the error without checking for formatted strings. This is the vulnerable function (pcnfsd version 1.2 source). from pcnfsd_print.c psrstat pr_start2(system, pr, user, fname, opts, id) ... ... if (rename(pathname, new_pathname)) { /* **--------------------------------------------------------------- ** Should never happen. **--------------------------------------------------------------- */ (void)sprintf(tempstr, "rpc.pcnfsd: spool file rename (%s->%s) failed.\n", pathname, new_pathname); msg_out(tempstr); <---- Vuln Function with our input form pcnfsd_xdr.c static _msgout(msg) char *msg; { #ifdef RPC_SVC_FG if (_rpcpmstart) syslog(LOG_ERR, msg); <---- Problem here! else (void) fprintf(stderr, "%s\n", msg); #else syslog(LOG_ERR, msg); <---- Problem here! #endif return(0); } GDB output: Program received signal SIGSEGV, Segmentation fault. 0xd01e28cc in _doprnt () from /usr/lib/libc.a(shr.o) (gdb) bt #0 0xd01e28cc in _doprnt () from /usr/lib/libc.a(shr.o) #1 0xd01dd4fc in vfprintf () from /usr/lib/libc.a(shr.o) #2 0xd024be10 in __syslog_r () from /usr/lib/libc.a(shr.o) #3 0xd024c400 in syslog () from /usr/lib/libc.a(shr.o) #4 0x10000d98 in ?? () CREDITS This vulnerability was discovered and exploited by Rodrigo Rubira Branco from Check Point Vulnerability Discovery Team (VDT).