Office-Word — CraftedSignal Threat Feed

CVE-2026-40367: Microsoft Office Word Untrusted Pointer Dereference Vulnerability

hello@craftedsignal.io — Tue, 12 May 2026 18:43:21 +0000

CVE-2026-40367 is an untrusted pointer dereference vulnerability affecting Microsoft Office Word. This vulnerability enables an unauthorized attacker to execute arbitrary code locally on a vulnerable system. The vulnerability stems from improper handling of memory pointers within the application, leading to a situation where a maliciously crafted document can trigger the dereference of an untrusted pointer. Successful exploitation allows attackers to gain control over the affected system, potentially leading to data theft, malware installation, or further unauthorized activities. This vulnerability poses a significant risk to organizations and individuals using Microsoft Office Word, as it can be exploited through social engineering tactics, such as distributing malicious documents via email or other communication channels.

Attack Chain

An attacker crafts a malicious Word document designed to trigger the untrusted pointer dereference vulnerability (CVE-2026-40367).
The attacker distributes the malicious document to a target user via email, shared network drive, or other means.
The target user opens the malicious document in Microsoft Office Word.
Upon opening the document, the vulnerable code path is triggered, causing the application to attempt to dereference an untrusted pointer.
The untrusted pointer dereference leads to the execution of arbitrary code within the context of the Word process.
The attacker leverages the code execution to install malware, establish persistence, or perform other malicious activities on the compromised system.
The attacker may attempt to escalate privileges or move laterally within the network, depending on the initial access level.

Impact

Successful exploitation of CVE-2026-40367 allows an attacker to execute arbitrary code on a target system with the privileges of the user running Microsoft Office Word. This can lead to complete system compromise, including data theft, malware installation, and denial of service. Given the widespread use of Microsoft Office Word, this vulnerability has the potential to affect a large number of users and organizations. If successful, an attacker could gain a foothold within an organization’s network and use it as a launching point for further attacks.

Recommendation

Apply the security update released by Microsoft to patch CVE-2026-40367 as soon as possible.
Deploy the provided Sigma rule to detect potential exploitation attempts targeting CVE-2026-40367.
Educate users on the risks of opening documents from untrusted sources to mitigate the risk of social engineering attacks.
Monitor process creation events for unusual or suspicious processes spawned by Microsoft Word, as indicated in the Sigma rule.

CVE-2026-40364: Microsoft Office Word Type Confusion Vulnerability

hello@craftedsignal.io — Tue, 12 May 2026 18:35:37 +0000

CVE-2026-40364 is a type confusion vulnerability in Microsoft Office Word that can lead to arbitrary code execution. An attacker could potentially exploit this vulnerability to execute code locally with the privileges of the current user. The vulnerability arises from improper handling of object types within Word, leading to memory corruption when processing specially crafted documents. While the specifics of exploitation are not detailed in the advisory, the high CVSS score and potential for local code execution make this a significant threat for systems running affected versions of Microsoft Office Word. Defenders should prioritize patching and consider implementing proactive detection measures to identify potential exploitation attempts.

Attack Chain

An attacker crafts a malicious Word document containing a payload designed to trigger the type confusion vulnerability (CVE-2026-40364).
The attacker delivers the crafted document to a target user via email, shared drive, or other means.
The user opens the malicious document in Microsoft Office Word.
Word attempts to process the document, triggering the type confusion vulnerability due to the incompatible object types.
The type confusion error leads to memory corruption within the Word process.
The attacker’s payload leverages the memory corruption to overwrite critical data structures.
The overwritten data structures are manipulated to redirect execution flow to attacker-controlled code.
The attacker achieves local code execution with the privileges of the user, potentially leading to further malicious actions.

Impact

Successful exploitation of CVE-2026-40364 allows an attacker to execute arbitrary code locally on a vulnerable system. The impact is significant, potentially allowing an attacker to install malware, steal sensitive data, or perform other malicious actions with the privileges of the logged-on user. Given the widespread use of Microsoft Office Word, this vulnerability poses a substantial risk to a large number of users and organizations.

Recommendation

Apply the security update released by Microsoft to patch CVE-2026-40364 as soon as possible (reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40364).
Deploy the Sigma rule “Detect Suspicious Process Creation from Winword.exe” to identify potential exploitation attempts.
Enable and review Microsoft Office’s Protected View settings to mitigate the risk of malicious documents.
Educate users about the risks of opening unsolicited or suspicious documents.

CVE-2026-40361: Microsoft Office Word Use-After-Free Vulnerability

hello@craftedsignal.io — Tue, 12 May 2026 18:34:49 +0000

CVE-2026-40361 is a use-after-free vulnerability affecting Microsoft Office Word. This vulnerability allows an unauthorized attacker to execute code locally on a vulnerable system. The vulnerability resides in how Word handles certain objects in memory. If an object is freed and later accessed again, it can lead to arbitrary code execution. An attacker could potentially exploit this vulnerability by crafting a malicious Word document that, when opened, triggers the use-after-free condition. Successful exploitation could allow the attacker to execute arbitrary code in the context of the current user. This poses a significant risk to organizations as it could lead to data breaches, malware infections, or system compromise.

Attack Chain

An attacker crafts a malicious Microsoft Word document containing a specially crafted object designed to trigger the use-after-free vulnerability (CVE-2026-40361).
The attacker delivers the malicious Word document to the victim via email or other means of file transfer.
The victim opens the malicious Word document using a vulnerable version of Microsoft Office Word.
Word attempts to process the crafted object within the document.
The vulnerability is triggered when Word attempts to access a memory location that has already been freed.
The attacker gains control of the program counter due to the use-after-free condition.
The attacker leverages this control to execute arbitrary code on the victim’s machine.
The attacker can then perform malicious actions such as installing malware, stealing sensitive data, or gaining further access to the network.

Impact

Successful exploitation of CVE-2026-40361 allows an attacker to execute arbitrary code locally on the victim’s machine. This could lead to a complete compromise of the affected system, including data theft, malware installation, and lateral movement within the network. Given the widespread use of Microsoft Office Word, this vulnerability poses a significant risk to a large number of users and organizations.

Recommendation

Deploy the Sigma rules provided in this brief to your SIEM to detect potential exploitation attempts.
Apply the security update provided by Microsoft to patch CVE-2026-40361 in Microsoft Office Word as soon as possible. Reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40361
Educate users about the risks of opening unsolicited or suspicious Word documents to mitigate the initial access vector.
Enable and monitor process creation logs on endpoints to detect suspicious processes spawned by Microsoft Word.