A recent discovery concerning a critical vulnerability, CVE-2024-23695, highlights a potential out-of-bounds write due to an integer overflow in cache_km.c's CacheOpPMRExec function. The impact of this vulnerability could lead to local escalation of privilege in the kernel without the need for additional execution privileges. Additionally, user interaction is not required to exploit this vulnerability. This post will examine the details of the vulnerability, provide code snippets, and examine potential exploit scenarios.

Vulnerability Details

In cache_km.c, the CacheOpPMRExec function has a possible out of bounds write due to an integer overflow. The issue lies in the incorrect handling of the "end" variable when performing cache operations. In particular, the calculation of "end" might lead to an integer overflow, causing an out-of-bounds write that may grant an attacker with escalated privileges.

The following code snippet demonstrates the vulnerability in CacheOpPMRExec()

static CacheError CacheOpPMRExec(CacheOpPMDParams *params)
{
  ...
  // Possible integer overflow in the calculation of "end"
  unsigned long end = start + size;

  if (start < params->range_start || end > params->range_end)
  {
    return CACHE_INVALID_RANGE;
  }

  // Out of bounds write, potentially leading to privilege escalation
  for (; start < end; start += PAGE_SIZE)
  {
    ...
  }
  ...
}

The vulnerability was first reported on the following platforms

1. GitHub Security Advisory
2. CVE Details
3. National Vulnerability Database (NVD)

Exploit Details

To exploit this vulnerability, an attacker would have to deliberately overflow the "end" variable, causing it to wrap around to an address lower than "start", leading to an out-of-bounds write. This can be achieved by manipulating the "size" input parameter when invoking CacheOpPMRExec(). The impact of this vulnerability can be severe, potentially allowing a malicious actor to overwrite sensitive kernel data and grant themselves escalated privileges.

Mitigation

Software developers are strongly advised to apply patches or updates that address CVE-2024-23695. The following steps should be taken to mitigate the vulnerability:

1. Carefully validate the user-supplied input parameters and add appropriate boundary checks to prevent integer overflow.
2. Modify CacheOpPMRExec() implementation to ensure proper handling of "end" variable, avoiding out-of-bounds write scenarios.

Conclusion

CVE-2024-23695 represents a significant security vulnerability that could lead to local escalation of privilege in the kernel without the need for additional execution privileges. Developers should ensure that patches or updates addressing the vulnerability are implemented as soon as possible. By understanding the details of this vulnerability and taking appropriate measures to mitigate it, security risks can be managed effectively.

Timeline

Published on: 07/09/2024 21:15:11 UTC
Last modified on: 07/12/2024 16:11:25 UTC