---------- Forwarded message ---------- Date: Wed, 17 Sep 2003 11:19:46 +0200 (CEST) From: Michal Zalewski <lcamtuf@dione.ids.pl> To: bugtraq at securityfocus.com, vulnwatch at securityfocus.com, full-disclosure at netsys.com Subject: [Full-Disclosure] Sendmail 8.12.9 prescan bug (a new one) [CAN-2003-0694] Hello lists, -------- Overview -------- There seems to be a remotely exploitable vulnerability in Sendmail up to and including the latest version, 8.12.9. The problem lies in prescan() function, but is not related to previous issues with this code. The primary attack vector is an indirect invocation via parseaddr(), although other routes are possible. Heap or stack structures, depending on the calling location, can be overwritten due to the ability to go past end of the input buffer in strtok()-alike routines. This is an early release, thanks to my sheer stupidity. -------------- Attack details -------------- Local exploitation on little endian Linux is confirmed to be trivial via recipient.c and sendtolist(), with a pointer overwrite leading to a neat case of free() on user-supplied data, i.e.: eip = 0x40178ae2 edx = 0x41414141 esi = 0x61616161 SEGV in chunk_free (ar_ptr=0x4022a160, p=0x81337e0) at malloc.c:3242 0x40178ae2 <chunk_free+486>: mov %esi,0xc(%edx) 0x40178ae5 <chunk_free+489>: mov %edx,0x8(%esi) Remote attack is believed to be possible. ---------------- Workaround / fix ---------------- Vendor was notified, and released an early patch attached below. There are no known workarounds. Index: parseaddr.c =================================================================== RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/parseaddr.c,v retrieving revision 1.16 diff -u -r1.16 parseaddr.c --- parseaddr.c 29 Mar 2003 19:44:01 -0000 1.16 +++ parseaddr.c 16 Sep 2003 17:37:26 -0000 @@ -700,7 +700,11 @@ addr[MAXNAME] = '\0'; returnnull: if (delimptr != NULL) + { + if (p > addr) + p--; *delimptr = p; + } CurEnv->e_to = saveto; return NULL; } -- ------------------------- bash$ :(){ :|:&};: -- Michal Zalewski * [http://lcamtuf.coredump.cx] Did you know that clones never use mirrors? --------------------------- 2003-09-16 21:18 -- -- Met vriendelijke groet, __________________ Sabri Berisha /\ ___/ SAB666-RIPE /- \ _/ Business Internet Trends BV http://www.bit.nl/~sabri /--- \/ __________________ _______________________________________________ Olympus mailing list ----- End forwarded message ----- -- Met vriendelijke groet, __________________ Sabri Berisha /\ ___/ SAB666-RIPE /- \ _/ Business Internet Trends BV http://www.bit.nl/~sabri /--- \/ __________________