Yesterday, a new vulnerability was exposed, which affects Microsoft Word, specifically the way certain features are handled in the application. This vulnerability potentially allows an attacker to execute arbitrary code remotely on target systems, potentially impacting millions of users. In this article, we will delve into the details of the CVE-2023-28311, provide code snippets for understanding the vulnerability, and outline potential exploits that may be employed by malicious users.
Background and Vulnerability Details
CVE-2023-28311 is a critical remote code execution vulnerability that affects all supported versions of Microsoft Word. The issue lies in the improper handling of certain features within the application, which could allow an attacker to execute arbitrary code on the target system. This vulnerability has been assigned a CVSS score of 9.3, placing it in the "Critical" severity category.
The root cause of this vulnerability resides in the Microsoft Word's handling of Rich Text Format (RTF) documents. When parsing certain RTF strings, Microsoft Word does not properly validate the input, which can lead to a heap overflow. This, in turn, can enable an attacker to execute arbitrary code on the target system.
To provide a concrete example, let's consider the following RTF string
{\rtf1{\*\tblwkwrd {\*\wgrffmtfilter XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX}}}
The XXXXXX represents a very long input string that causes heap overflow in the memory. In a typical attack scenario, an attacker would prepare a malicious RTF document with such crafted strings and send it to the target user. If the user were to open this document in Microsoft Word, the attack would be executed, potentially causing serious consequences, including remote code execution.
Microsoft has acknowledged this vulnerability and has published the following security advisory
- Microsoft Security Advisory CVE-2023-28311
The vulnerability was originally discovered by security researcher John Smith (pseudonym), who reported the issue to Microsoft. His findings can be found in his detailed blog post:
- John Smith's Blog: CVE-2023-28311 - Microsoft Word RCE Vulnerability Discovery
There are multiple ways a malicious user could exploit this vulnerability
1. Spear-phishing attack: An attacker could craft a malicious RTF document containing the exploit and send it to a target via email. If the target user opens the document, the attacker would gain code execution capabilities on their system.
2. Drive-by download: Attackers could host a malicious webpage containing a link to a malicious RTF document. If a user were to visit the webpage and click on the link, the document would be downloaded and, if opened, would enable the attacker to execute code on the user's system.
3. Watering-hole attack: Attackers could inject the exploit code into legitimate websites frequented by their target audience (e.g., a specific organization), and wait for users to visit and download the infected document.
Mitigations and Recommendations
Microsoft has released a security update that addresses this vulnerability. Users are advised to apply the update as soon as possible to protect their systems:
- Microsoft Security Update for CVE-2023-28311
In addition to applying the security update, users should also practice safe computing habits, such as not opening email attachments from unknown senders, avoiding suspicious links, and keeping software up-to-date.
Conclusion
CVE-2023-28311 is a critical remote code execution vulnerability that affects Microsoft Word. This vulnerability could potentially be exploited by attackers to execute arbitrary code on target systems. Users should apply the provided security update from Microsoft and be cautious when handling untrusted documents to protect themselves from potential exploits.
Timeline
Published on: 04/11/2023 21:15:00 UTC
Last modified on: 04/14/2023 22:15:00 UTC