CVE-2020-3853 - Access of Resource Using Incompatible Type ('Type Confusion')

Severity

78%

Complexity

18%

Confidentiality

98%

A type confusion issue was addressed with improved memory handling. This issue is fixed in iOS 13.3.1 and iPadOS 13.3.1, macOS Catalina 10.15.3, tvOS 13.3.1, watchOS 6.1.2. A malicious application may be able to execute arbitrary code with system privileges.

A type confusion issue was addressed with improved memory handling. This issue is fixed in iOS 13.3.1 and iPadOS 13.3.1, macOS Catalina 10.15.3, tvOS 13.3.1, watchOS 6.1.2. A malicious application may be able to execute arbitrary code with system privileges.

CVSS 3.1 Base Score 7.8. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).

CVSS 2.0 Base Score 9.3. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:C/I:C/A:C).

Demo Examples

Access of Resource Using Incompatible Type ('Type Confusion')

CWE-843

Access of Resource Using Incompatible Type ('Type Confusion')

CWE-843

Access of Resource Using Incompatible Type ('Type Confusion')

CWE-843

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).


               
print "\$UserPrivilegeArray = $UserPrivilegeArray\n";
print "Regular user!\n";
print "Admin!\n";

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.

Since the logic also "fails open" (CWE-636), the result of this bug is that all users are assigned administrator privileges.

While this is a forced example, it demonstrates how type confusion can have security consequences, even in memory-safe languages.

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