CVE-2026-80087 in Office
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to disclose information over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a heap-based buffer overflow within the core processing components of Microsoft Office, specifically affecting how memory is allocated and managed during the parsing or rendering of specific document types. In this type of flaw, the application fails to properly validate user-supplied input before copying it into a pre-allocated block of memory on the heap. When an attacker crafts a malicious file containing oversized data structures or specially formatted objects that exceed the expected buffer limits, the excess data spills over into adjacent memory regions. This overwrite corrupts critical metadata associated with heap allocations, such as size fields and pointers to other allocated blocks. The immediate technical consequence is the corruption of internal application state, which can lead to unpredictable behavior including crashes, but more critically in this context, it allows for arbitrary read or write operations depending on how the corrupted memory is subsequently accessed by the Office application logic.
The operational impact centers on unauthorized information disclosure over a network, indicating that the vulnerability likely resides within components responsible for handling remote content or files retrieved from untrusted sources such as email attachments, shared drives, or web-based document viewers like Microsoft Office Online. By exploiting this heap overflow, an attacker can manipulate memory contents to leak sensitive data stored in adjacent buffers. This could include credentials cached by the application, session tokens, encryption keys used for local storage, or proprietary content from other open documents within the same process space. The ability to disclose information over a network suggests that the vulnerability may be triggered when Office processes files fetched via HTTP/HTTPS protocols, potentially allowing remote attackers to exfiltrate data without requiring direct file system access on the victim's machine. This transforms what might otherwise be a local denial-of-service or code execution risk into a significant confidentiality breach with potential implications for corporate espionage and identity theft.
From a classification perspective, this vulnerability aligns closely with CWE-122: Heap-based Buffer Overflow, which describes writing data beyond the bounds of a heap allocated buffer. The exploitation technique often involves manipulating object headers to achieve arbitrary memory reads or writes, falling under ATT&CK Tactic TA0005 (Defense Evasion) and specifically techniques related to Memory Manipulation such as T1074: Data Staged or T1083: File and Directory Discovery if the leaked data is used for further reconnaissance. The network-based nature of the disclosure also touches upon ATT&CK technique T1048: Exfiltration Over Alternative Protocol, where sensitive information is extracted through standard web traffic to evade detection by traditional security monitoring tools that focus on malicious file execution rather than memory corruption artifacts.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary defense is the prompt application of vendor-provided patches or updates released by Microsoft Office vendors, which typically include bounds checking fixes and improved input validation routines within the affected components. Organizations should enforce strict email filtering policies to block attachments from unknown senders and disable automatic previewing of potentially malicious file types in Outlook and other clients until they are opened explicitly by the user. Additionally, enabling Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR) can mitigate exploitation attempts by making it harder for attackers to predict memory layouts or execute injected code, although these controls do not prevent information disclosure directly. Security awareness training should emphasize caution when opening documents from untrusted sources, particularly those containing macros or embedded objects that trigger complex rendering engines within Office applications.