A critical vulnerability (CVE-2022-20803) has been identified in the OLE2 (Object Linking & Embedding) file parser of Clam AntiVirus (ClamAV) affecting versions .104. through .104.2. This vulnerability can allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device. This post aims to provide an in-depth analysis of the vulnerability, its potential impact, and recommended mitigations.
Vulnerability Details
The vulnerability is a double-free issue that occurs due to the incorrect usage of the realloc function in ClamAV's OLE2 file parser. Here is a code snippet showcasing the improper usage of realloc in the affected versions:
char *buffer = (char *)malloc(size1);
...
buffer = (char *)realloc(buffer, size2);
...
free(buffer);
In this code snippet, when 'realloc' is called to adjust the size of the buffer, it may internally call 'free' to release the old memory before allocating new memory. This can cause a double-free error if the free function is called again later.
An attacker can exploit this vulnerability by crafting a malicious OLE2 file and submitting it to a ClamAV scanning process on the targeted device. Successful exploitation can lead to the crash of the scanning process, resulting in a DoS condition.
Official References
The vulnerability has been officially reported by the ClamAV team on their blog:
Official ClamAV Blog Post
ClamAV GitHub Repository
Exploit Details
Currently, there are no publicly available exploits for this vulnerability. However, potential attackers can still create their custom exploits by analyzing the vulnerable code and crafting specific OLE2 files capable of triggering this double-free error during the ClamAV scanning. This could lead to a more widespread exploitation of the CVE-2022-20803 vulnerability.
Mitigation and Recommendations
To prevent exploitation of this vulnerability, the affected users should immediately update ClamAV to the latest security-patched version (.104.3). The ClamAV team has provided a fix for the issue by properly handling the realloc function and managing memory allocations. The update effectively eliminates the chances of a double-free error in the OLE2 file parser.
In addition to updating ClamAV, users should always exercise caution when scanning unknown files and follow the best security practices to minimize the risks associated with software vulnerabilities.
Conclusion
The CVE-2022-20803 vulnerability in ClamAV's OLE2 file parser is a serious threat that can cause denial of service conditions on affected devices. By understanding the details of the vulnerability, its impact, and possible attack scenarios, users can take the necessary steps to protect their systems. Regularly updating software to the latest security-patched versions and implementing recommended mitigation strategies are essential to ensure system security.
Stay informed about CVE-2022-20803 and other relevant software vulnerabilities to safeguard your devices and data against potential attacks.
Timeline
Published on: 02/17/2023 18:15:00 UTC
Last modified on: 02/28/2023 16:22:00 UTC