Heap buffer overflow vulnerabilities are quite a challenge for security analysts and software developers alike. They can cause serious security flaws, expose sensitive data, or even allow attackers to execute malicious code on vulnerable systems. In this post, we will dig deep into a specific heap buffer overflow vulnerability (CVE-2022-44840) affecting the popular 'binutils' package, specifically its 'readelf' utility. We will investigate the causes behind this vulnerability, understand how it can be exploited, and look at the relevant code snippets in detail.
Background
'binutils' is a collection of binary tools widely used in the Unix/Linux ecosystem. It includes utilities like 'as', 'ld', 'nm', 'objdump', and 'readelf'. The vulnerability in question affects 'readelf', which is a tool used to display various information about ELF (Executable and Linkable Format) files. It is of great importance to developers and reverse engineers working with ELF files.
The vulnerability in question (CVE-2022-44840) is a heap buffer overflow present in readelf, specifically in the function 'find_section_in_set' in the 'readelf.c' source file. This vulnerability was discovered in binutils packages before version 2.40.
Original References
1. Vulnerability Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-44840
2. Mailing List Archive: https://www.sourceware.org/ml/binutils/2016-06/msg00076.html
3. Official Patch: http://git.savannah.gnu.org/cgit/binutils.git/commit/?id=d246037e21c5afc229d2bbcdc3241ef17ea7ff
How does the Heap Buffer Overflow occur?
The specific function where the vulnerability lies is 'static Elf_Internal_Shdr * find_section_in_set (struct section_set const * section_set, unsigned int unshndx)' in the 'readelf.c' file. The purpose of this function is to help find a specific section in a set of sections. The set is represented by an array of pointers to 'Elf_Internal_Shdr' objects, and the length of this array is an unsigned integer stored in 'section_set.num_sections'. The 'unshndx' argument is used as an index to look up the desired section in this array.
Now, let's look at the vulnerable part of the function
if (unshndx < section_set->num_sections)
{
return section_set->sections[unshndx];
}
This conditional statement checks whether the given index 'unshndx' is within the bounds of the 'section_set->sections' array. If the index is within bounds, the function returns a pointer from the 'sections' array at that index. However, if an attacker can send a specially crafted ELF file having an invalid index value (greater than or equal to 'section_set->num_sections'), the above conditional statement will fail the bounds check.
As a result, when the function tries to access 'section_set->sections[unshndx]', it will access memory outside the bounds of the 'sections' array, causing a heap buffer overflow. This can potentially lead to arbitrary code execution, system crashes, or other undefined behavior.
Exploiting the Vulnerability
For an attacker to exploit this vulnerability successfully, they need to craft a malicious ELF file in such a way that it passes all other sanity checks in the 'readelf' utility but triggers the heap overflow when 'find_section_in_set()' is called with a malicious index. This would require a deep understanding of the ELF file format and the internal workings of the 'readelf' utility.
Possible exploitation scenarios include an attacker hosting a malicious ELF file on a web server, peering into a network share, or sending emails with the file as an attachment. When a target user tries to analyze the malicious ELF file using 'readelf', the vulnerable system could be compromised, leading to various security breaches.
Patch and Mitigation
The official patch for this vulnerability is available at the following link: http://git.savannah.gnu.org/cgit/binutils.git/commit/?id=d246037e21c5afc229d2bbcdc3241ef17ea7ff
By applying this patch, the out-of-bounds access in the 'find_section_in_set()' function is prevented, thus eliminating the heap overflow vulnerability.
It is vital that users of the 'binutils' package, especially the 'readelf' utility, immediately update to version 2.40 or higher. Furthermore, it's recommended to analyze untrusted ELF files in a secure, isolated environment to prevent potential exploitation of any undiscovered vulnerabilities.
Conclusion
This post gave an in-depth analysis of the heap buffer overflow vulnerability CVE-2022-44840, affecting the 'readelf' utility in 'binutils' package before version 2.40. By understanding how this vulnerability occurs, its potential impact, and steps to patch or mitigate it, we can contribute to a more secure software ecosystem.
Timeline
Published on: 08/22/2023 19:16:00 UTC
Last modified on: 08/26/2023 02:14:00 UTC