In today's post, we will investigate a recently discovered stack overflow vulnerability, CVE-2022-44079, which affects the pycdc project, a Python bytecode disassembler and decompiler. The issue was identified in commit 44a730f3a889503014fec94ae6e62d8401cb75e5 of the project and involves the component __sanitizer::StackDepotBase<__sanitizer::StackDepotNode.

For context, stack overflow vulnerabilities occur when excessive data is written to a particular section of memory, causing data to overwrite adjacent sections. Attackers can exploit this to overwrite other parts of an application's memory, potentially leading to arbitrary code execution or application crashes.

Exploit Details

Link to the vulnerable commit: Commit 44a730f3a889503014fec94ae6e62d8401cb75e5

The vulnerability resides in the function __sanitizer::StackDepotPut in file sanitizer_common/sanitizer_stackdepotbase.h:

template <class T>
u32 StackDepotBase<T>::Put(T *stack, StackDepotHandle **handle) {
  if (!stack)
    return ;
  uptr stack_id = stack->hash();
  if (handle)
    *handle = nullptr;
  ...
}

The problem occurs due to an unchecked pointer dereference, which may lead to a stack overflow if the pointer received points to a null value or an invalid memory location.

An attacker could potentially exploit this issue by providing a custom-crafted input to the function, which results in stack exhaustion and possible execution of arbitrary code.

How to Mitigate and Patch

The pycdc maintainers have acknowledged the vulnerability, and a patch has been proposed to fix the issue. The proposed patch adds a validation check to ensure that the pointer is not null, reducing the chance of a stack overflow vulnerability.

The following code snippet shows the updated version of the function with the added validation check

template <class T>
u32 StackDepotBase<T>::Put(T *stack, StackDepotHandle **handle) {
  if (!stack)
    return ;

  // Ensure that the input pointer is not null and has a valid address.
  if (stack == nullptr || stack <= (T *)x)
    return ;

  uptr stack_id = stack->hash();
  if (handle)
    *handle = nullptr;
  ...
}

To protect any installations of pycdc that may contain this vulnerability, it is recommended to apply this patch or update to the latest version of pycdc, where the issue has been fixed. You can find the latest version of pycdc at the following link: pycdc latest release

Conclusion

CVE-2022-44079 is a stack overflow vulnerability discovered in pycdc's commit 44a730f3a889503014fec94ae6e62d8401cb75e5. Attackers can exploit this issue to cause a denial of service or potentially execute arbitrary code. The vulnerability can be mitigated by applying the proposed patch or updating to the latest version of pycdc, which contains the necessary fix.

Timeline

Published on: 10/31/2022 19:15:00 UTC
Last modified on: 03/02/2023 16:39:00 UTC