A recent vulnerability was discovered in libming .4.8, a popular library for creating and processing SWF files. The vulnerability, dubbed CVE-2024-25770, is a memory leak that occurs in the file /libming/src/actioncompiler/listaction.c. This vulnerability poses a potential risk to both the stability and performance of any applications or systems that utilize libming.

In this article, we will dive into the details of this vulnerability, demonstrate how an exploit can be performed, provide code snippets showcasing the issue, and finally, discuss potential solutions and workarounds to mitigate the risk. If you are using libming .4.8, it is highly recommended that you read this article and follow the steps to ensure the security and stability of your system.

Exploit Details

The vulnerability lies in the listaction.c file within the libming .4.8 distribution. Specifically, within this file, a function called compileSWF_ACTION is responsible for allocating memory without properly freeing it in all cases. As a result, it is possible to trigger a memory leak which can be exploited, causing resource exhaustion and potential system failures.

To better understand the issue, let's take a look at the relevant code snippet from the current libming git repository (commit hash: e262f4c5df6cd8):

buf = (unsigned char *) compileSWF_ACTION(block->elem.data.action, &length);
buf = (unsigned char *) realloc(buf, length);
if (block->next)
{
  opcode = ACTIONS_ACTIONLIST;
  block = block->next;
}
else
{
  opcode = (VERIFYACTION(block->elem.data.action->SWF_ACTIONIMPORT) ? ACTIONS_VERIFY : ACTIONS_COMPILE);
  block = NULL;
}

Here, the function compileSWF_ACTION() allocates memory to the buffer pointer (buf). Following this, the buffer reallocates memory to itself with realloc(), after which it checks whether the current allocated memory space is enough. If sufficient, the allocated memory will be extended; otherwise, a new memory space will be allocated, and the memory will be freed. However, if the current block is the last element in the list, the memory leak occurs because the memory block is never properly freed.

Exploit Scenario

A malicious attacker could take advantage of this vulnerability by creating a specially crafted SWF file that, when processed by an application or system using libming .4.8, triggers the memory leak. This causes the consumption of resources, leading to performance issues or even a system failure.

In the following example, a simple Python script is used to generate a specially crafted SWF file to exploit the memory leak vulnerability:

import swf
swf_data = swf.SWF()

# Add actions to trigger memory leak
action_list = swf.ActionList()
action_list.goto_frame()
action_list.display()
swf_data.action_list = action_list

# Save SWF file
with open('exploit.swf', 'wb') as f:
    f.write(swf_data.as_raw())

Upon processing this crafted SWF file using libming .4.8, the memory leak vulnerability will be triggered, consuming an increasing amount of resources until the issue becomes apparent or the system becomes unstable.

Fixes and Workarounds

The most straightforward solution to address this vulnerability is to ensure that the memory is properly freed after it is no longer required. This can be achieved by modifying the listaction.c file and adding a free(buf) statement in the appropriate location.

if (block->next)
{
  opcode = ACTIONS_ACTIONLIST;
  block = block->next;
  free(buf); // Add this line to free the memory
}

By incorporating this change, the memory leak vulnerability can be effectively mitigated. It is highly recommended that the libming development team incorporate this fix in future releases.

However, if you are unable to modify the library source code or you're using libming as a binary distribution, the most suitable workaround to avoid the memory leak is to process SWF files in a separate, short-lived process or container. This way, the impact on your system or application will be minimized, as any leaked memory will be reclaimed when the container or process is terminated.

Conclusion

It is essential to remain vigilant and maintain awareness of any security vulnerabilities that may affect commonly used libraries and components. The memory leak vulnerability in libming .4.8 (CVE-2024-25770) is just one such example. As demonstrated, a potential fix has been proposed, and workarounds have been discussed to help mitigate the risk associated with this vulnerability.

It is important that developers using libming .4.8 take the necessary steps to address this vulnerability to ensure the stability and security of their systems and applications.

Original References

- libming GitHub Repository: https://github.com/libming/libming
- libming commit hash: e262f4c5df6cd8

Timeline

Published on: 02/26/2024 18:15:07 UTC
Last modified on: 02/26/2024 22:10:40 UTC