The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
When the product accesses the resource using an incompatible type, this could trigger logical errors because the resource does not have expected properties. In languages without memory safety, such as C and C++, type confusion can lead to out-of-bounds memory access. While this weakness is frequently associated with unions when parsing data with many different embedded object types in C, it can be present in any application that can interpret the same variable or memory location in multiple ways. This weakness is not unique to C and C++. For example, errors in PHP applications can be triggered by providing array parameters when scalars are expected, or vice versa. Languages such as Perl, which perform automatic conversion of a variable of one type when it is accessed as if it were another type, can also contain these issues.
Threat Mapped score: 1.8
Industry: Finiancial
Threat priority: P4 - Informational (Low)
CVE: CVE-2010-4577
Type confusion in CSS sequence leads to out-of-bounds read.
CVE: CVE-2011-0611 — KEV
Size inconsistency allows code execution, first discovered when it was actively exploited in-the-wild.
CVE: CVE-2010-0258
Improperly-parsed file containing records of different types leads to code execution when a memory location is interpreted as a different object than intended.
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| Phase | Note |
|---|---|
| Implementation | N/A |
Intro: The following code uses a union to support the representation of different types of messages. It formats messages differently, depending on their type.
Body: The code intends to process the message as a NAME_TYPE, and sets the default message to "Hello World." However, since both buf.name and buf.nameID are part of the same union, they can act as aliases for the same memory location, depending on memory layout after compilation.
#define NAME_TYPE 1 #define ID_TYPE 2 struct MessageBuffer { int msgType; union { char *name; int nameID; }; }; int main (int argc, char **argv) { struct MessageBuffer buf; char *defaultMessage = "Hello World"; buf.msgType = NAME_TYPE; buf.name = defaultMessage; printf("Pointer of buf.name is %p\n", buf.name); /* This particular value for nameID is used to make the code architecture-independent. If coming from untrusted input, it could be any value. */ buf.nameID = (int)(defaultMessage + 1); printf("Pointer of buf.name is now %p\n", buf.name); if (buf.msgType == NAME_TYPE) { printf("Message: %s\n", buf.name); } else { printf("Message: Use ID %d\n", buf.nameID); } }Intro: The following PHP code accepts a value, adds 5, and prints the sum.
Body: When called with the following query string:
$value = $_GET['value']; $sum = $value + 5; echo "value parameter is '$value'<p>"; echo "SUM is $sum";Intro: The following Perl code is intended to look up the privileges for user ID's between 0 and 3, by performing an access of the $UserPrivilegeArray reference. It is expected that only userID 3 is an admin (since this is listed in the third element of the array).
Body: In this case, the programmer intended to use "$UserPrivilegeArray->{$userID}" to access the proper position in the array. But because the subscript was omitted, the "user" string was compared to the scalar representation of the $UserPrivilegeArray reference, which might be of the form "ARRAY(0x229e8)" or similar.
my $UserPrivilegeArray = ["user", "user", "admin", "user"]; my $userID = get_current_user_ID(); if ($UserPrivilegeArray eq "user") { print "Regular user!\n"; } else { print "Admin!\n"; } print "\$UserPrivilegeArray = $UserPrivilegeArray\n";