Attack Chain

1. Attacker crafts a malicious Microsoft Word document designed to trigger the use-after-free vulnerability (CVE-2026-23657).
2. The attacker delivers the malicious document to the victim, likely via email or shared file storage.
3. The victim opens the malicious document in Microsoft Word.
4. The crafted document exploits a weakness in memory management, freeing a memory region while a pointer to it is still in use.
5. The attacker leverages the use-after-free condition to overwrite the freed memory with attacker-controlled data.
6. Upon dereferencing the dangling pointer, the corrupted data is executed, leading to code execution.
7. The attacker executes arbitrary code within the context of the user running Microsoft Word.
8. The attacker may then install malware, steal sensitive information, or establish a persistent foothold on the compromised system.

Impact

Successful exploitation of CVE-2026-23657 allows an attacker to execute arbitrary code on a vulnerable system with the privileges of the user running Microsoft Word. This can lead to the installation of malware, theft of sensitive data, and further compromise of the system and network. The impact of this vulnerability is significant, as Microsoft Word is widely used in organizations of all sizes, making it a valuable target for attackers. The potential for arbitrary code execution elevates this vulnerability to a high-risk level, demanding immediate attention from security teams.

Recommendation

• Apply the patch released by Microsoft to address CVE-2026-23657 on all systems running Microsoft Office Word. (Reference: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-23657)
• Deploy the Sigma rule Detect Suspicious Word Child Process to detect potentially malicious processes spawned by Microsoft Word.
• Enable process creation logging to capture process execution events, ensuring the Sigma rule has the necessary data to function.