CVE-2023-40166 - Heap Buffer Read Overflow in Notepad++ `FileManager::detectLanguageFromTextBegining` Function

Notepad++ is a popular free and open-source source code editor. A vulnerability has been discovered in versions 8.5.6 and earlier, which may result in a heap buffer read overflow in the FileManager::detectLanguageFromTextBegining function. This post will detail the exploit, relevant code snippets, and links to original references for further information.

>> _NOTE: The exploitability of this vulnerability remains unclear. It is possible that it could be used to leak internal memory allocation information, although no known patches are currently available._

Vulnerability Details

The discovered vulnerability is identified as CVE-2023-40166 and impacts Notepad++ versions 8.5.6 and prior. The vulnerability arises from an incorrectly configured buffer size in the FileManager::detectLanguageFromTextBegining function, which may result in heap buffer read overflow.

Let's take a look at the relevant code snippet for this vulnerability

void FileManager::detectLanguageFromTextBegining(Buffer *buf)
{
    // ... (other code)

	const int nbCharRead = 128;
	char data[nbCharRead];
	doc.getCharRange(data, , nbCharRead);
	data[nbCharRead - 1] = '\';

	// ... (other code)
	
	for (int i = ; i < langsToCheck; ++i)
	{
		int docLang = (isCompatible[i] && !_tcscmp(data, langEncode[i]))?-1:i;
		if (docLang != -1)
		{
			// ... (other code)
		}
	}
}

The issue occurs when reading 128 characters (nbCharRead) from the document and storing them in the data buffer. The buffer size is fixed at 128 characters and doesn't take into account any null-termination character. This means that if the document contains more than 128 characters, a heap buffer read overflow will occur.

Exploit Details

As mentioned earlier, the exploitability of this vulnerability remains unclear. However, we can speculate on possible attack scenarios based on the nature of the issue.

1. _Memory Leak_: Given the heap buffer read overflow, it may be possible for an attacker to craft a malicious document that triggers the vulnerability and leaks internal memory allocation information. This information could then be used to mount further attacks.

2. _Denial of Service_: If the attacker can repeatedly trigger the vulnerability, it may cause instability or crashes in Notepad++, impacting its availability to users.

As of the time of this publication, no known patches or mitigations are available in existing versions of Notepad++. The developer team should consider adjusting the buffer size and validation of the detectLanguageFromTextBegining function to prevent the heap buffer read overflow from occurring.

References

- [Notepad++] (https://notepad-plus-plus.org/)
- [CVE Details - CVE-2023-40166] (https://www.cvedetails.com/cve/CVE-2023-40166/)

Conclusion

In summary, a heap buffer read overflow vulnerability has been discovered in Notepad++ versions 8.5.6 and earlier. Although the exploitability of this vulnerability is unclear, it is important for Notepad++ developers and users to be aware of the issue and potential attack scenarios. Currently, there are no known patches available, but developers should consider adjusting the buffer size and validation to mitigate the issue.

Timeline

Published on: 08/25/2023 21:15:00 UTC
Last modified on: 08/31/2023 16:33:00 UTC