Tremor is an event processing system for unstructured data. A vulnerability exists between versions 0.7.2 and 0.11.6. This vulnerability is a memory safety Issue when using patch or merge on state and assign the result back to state. In this case, affected versions of Tremor and the tremor-script crate maintains references to memory that might have been freed already. And these memory regions can be accessed by retrieving the state, e.g. send it over TCP or HTTP. This requires the Tremor server (or any other program using tremor-script) to execute a tremor-script script that uses the mentioned language construct. The issue has been patched in version 0.11.6 by removing the optimization and always cloning the target expression of a Merge or Patch. If an upgrade is not possible, a possible workaround is to avoid the optimization by introducing a temporary variable and not immediately reassigning to state.
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 |
|---|---|---|---|
| Tremor | Linuxfoundation | 0.7.2 (including) | 0.11.6 (excluding) |
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.