CVE-2026-78525 in Office
Summary
by MITRE • 09/09/2026
Use after free in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Outlook application, specifically involving a use-after-free condition that can be exploited by an unauthorized actor to achieve remote code execution via network-based attacks. This type of defect arises when software continues to reference a memory block after it has been freed or deallocated by the system. In the context of Outlook, this typically occurs during the processing of specially crafted email messages or calendar items where the application allocates memory for specific data structures and subsequently releases that memory while retaining pointers to it. When the attacker triggers operations on these dangling pointers, the program may read from or write to arbitrary locations in memory, leading to unpredictable behavior that can be manipulated to execute malicious code with the privileges of the current user.
From a technical perspective, use-after-free vulnerabilities are particularly dangerous because they allow attackers to control the content of freed memory through heap spraying techniques or by manipulating object lifecycles within the application's internal data structures. By carefully crafting input such as malformed HTML in email bodies or specific MAPI properties, an attacker can cause Outlook to free a critical object and then immediately access it again before the operating system reclaims that space for other purposes. This allows the injection of shellcode into the memory region previously occupied by the legitimate object. When the application attempts to use this corrupted pointer, control flow is redirected to the injected code, enabling full compromise of the affected system. The network vector implies that no physical access or local user interaction beyond opening a malicious email is required, significantly lowering the barrier for exploitation and increasing the risk profile substantially.
The operational impact of successfully exploiting this vulnerability extends far beyond simple data exposure. An attacker who gains remote code execution capabilities can install programs, view, change, or delete data, and create new accounts with full user rights on the compromised machine. This effectively grants the adversary complete control over the victim's workstation, which often serves as a gateway into larger corporate networks if Outlook is used for business communications. The ability to execute code remotely makes this vulnerability a prime target for automated worm-like propagation or targeted spear-phishing campaigns aimed at high-value individuals within an organization. Furthermore, because Microsoft Office applications are deeply integrated with Windows operating systems and Active Directory environments, the compromise of one endpoint can facilitate lateral movement, privilege escalation, and persistent access across the enterprise infrastructure.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary defense is to apply the latest security updates provided by Microsoft as soon as they become available, ensuring that patches for known use-after-free flaws in Outlook are installed promptly. Organizations should also implement strict email filtering policies using advanced threat protection solutions capable of detecting and quarantining suspicious attachments or embedded scripts before they reach end-user mailboxes. Additionally, enabling Protected View features within Office applications can sandbox potentially unsafe content, preventing active code execution until the user explicitly trusts the source. Network segmentation and endpoint detection and response tools should be deployed to monitor for anomalous behavior indicative of exploitation attempts, such as unusual process creation or memory access patterns following email receipt. Regular security awareness training is also essential to reduce the likelihood of users interacting with malicious content despite technical controls.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-416, which defines use-after-free errors where a pointer references freed memory that may have been reallocated for different purposes. In terms of offensive cyber operations and threat modeling, this exploit technique corresponds to the MITRE ATT&CK framework's Tactic 0003 Persistence or Tactic 0005 Defense Evasion depending on how the code is maintained post-exploitation, but more directly relates to Initial Access vectors involving spear-phishing attachments if delivered via email. Understanding these mappings helps security teams prioritize patching efforts and configure detection rules based on established industry standards for vulnerability classification and adversary behavior modeling.