An exploitable vulnerability exists in the cross-reference table repairing functionality of Nitro Software, Inc.’s Nitro Pro 13.13.2.242. While searching for an object identifier in a malformed document that is missing from the cross-reference table, the application will save a reference to the object’s cross-reference table entry inside a stack variable. If the referenced object identifier is not found, the application may resize the cross-reference table which can change the scope of its entry. Later when the application tries to reference cross-reference entry via the stack variable, the application will access memory belonging to the recently freed table causing a use-after-free condition. A specially crafted document can be delivered by an attacker and loaded by a victim in order to trigger this vulnerability.
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Nitro_pro | Gonitro | 13.13.2.242 (including) | 13.13.2.242 (including) |
| Nitro_pro | Gonitro | 13.16.2.300 (including) | 13.16.2.300 (including) |
The use of previously-freed memory can have any number of adverse consequences, ranging from the corruption of valid data to the execution of arbitrary code, depending on the instantiation and timing of the flaw. The simplest way data corruption may occur involves the system’s reuse of the freed memory. Use-after-free errors have two common and sometimes overlapping causes:
In this scenario, the memory in question is allocated to another pointer validly at some point after it has been freed. The original pointer to the freed memory is used again and points to somewhere within the new allocation. As the data is changed, it corrupts the validly used memory; this induces undefined behavior in the process. If the newly allocated data happens to hold a class, in C++ for example, various function pointers may be scattered within the heap data. If one of these function pointers is overwritten with an address to valid shellcode, execution of arbitrary code can be achieved.