[Full-disclosure] Mercur SP4 IMAPD

The attached exploits several signedness bugs in the NTLM implementation
of Mercur IMAPD (www.atrium-software.com) to give the attacker
complete control over a memcpy to a stack variable… (non-authenticated)
In this case, memcpy(buf, src+a, b) with 'a', and 'b' being user controlled
and buf ~7208 bytes.

note due to the most important signedness issue, we can only control 'a' within
the range -65535 < a < 65536…

The result of the PoC is an simple crash trying to copy 0xffffffff bytes…

(d94.1dc): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=0210a108 ebx=0210ac24 ecx=3fffeb08 edx=ffffffff esi=02110000 edi=0210f4e4
eip=0042e0d3 esp=021098c8 ebp=021098d0 iopl=0 nv up ei pl nz na pe cy
cs=001b ss=0023 ds=0023 es=0023 fs=003b gs=0000 efl=00010207
*** WARNING: Unable to verify checksum for C:\Program Files\MERCUR\mcrimap4.exe
*** ERROR: Symbol file could not be found. Defaulted to export symbols for C:\Program Files\MERCUR\mcrimap4.exe -
mcrimap4!_GetExceptDLLinfo+0x2d05f:
0042e0d3 f3a5 rep movs dword ptr es:[edi],dword ptr [esi] es:0023:0210f4e4=00000000 ds:0023:02110000=???

PoC: http://www.digit-labs.org/files/exploits/mercur-v1.pl

mu-b
([email protected])

"Only a few people will follow the proof. Whoever does will
spend the rest of his life convincing people it is correct."
- Anonymous, "P ?= NP"

Full-Disclosure - We believe in it.
Charter: http://lists.grok.org.uk/full-disclosure-charter.html
Hosted and sponsored by Secunia - http://secunia.com/