{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata. Fed continuously.","feed_url":"https://feed.craftedsignal.io/tags/cve-2026-40363/feed.json","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cpes":[],"_cs_cves":[{"cvss":8.4,"id":"CVE-2026-40363"}],"_cs_exploited":false,"_cs_has_poc":false,"_cs_poc_references":[],"_cs_products":["Office"],"_cs_severities":["high"],"_cs_tags":["heap-based buffer overflow","code execution","microsoft office","cve-2026-40363"],"_cs_type":"threat","_cs_vendors":["Microsoft"],"content_html":"\u003cp\u003eCVE-2026-40363 is a heap-based buffer overflow vulnerability affecting Microsoft Office. An unauthorized attacker could exploit this vulnerability to execute arbitrary code on a local system. The vulnerability stems from improper memory management within the Office suite when handling specific file formats or data structures. Successful exploitation of this vulnerability could allow an attacker to gain control of the affected system, potentially leading to data theft, system compromise, or further malicious activities. Defenders should prioritize patching this vulnerability to prevent potential exploitation.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker crafts a malicious document (e.g., Word, Excel, PowerPoint) specifically designed to trigger the heap-based buffer overflow within Microsoft Office.\u003c/li\u003e\n\u003cli\u003eThe attacker convinces a user to open the malicious document locally via social engineering.\u003c/li\u003e\n\u003cli\u003eMicrosoft Office attempts to parse the malicious document, leading to the heap-based buffer overflow when handling a specific data structure.\u003c/li\u003e\n\u003cli\u003eThe buffer overflow allows the attacker to overwrite memory on the heap, potentially corrupting critical data structures or injecting malicious code.\u003c/li\u003e\n\u003cli\u003eThe attacker leverages the memory corruption to gain control of the program counter and redirect execution flow to the injected malicious code.\u003c/li\u003e\n\u003cli\u003eThe injected code executes with the privileges of the Microsoft Office application.\u003c/li\u003e\n\u003cli\u003eThe attacker can now perform arbitrary actions on the local system, such as installing malware, stealing sensitive data, or creating new user accounts.\u003c/li\u003e\n\u003cli\u003eThe attacker achieves their objective, such as gaining persistent access to the system or exfiltrating sensitive data.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful exploitation of CVE-2026-40363 allows a local attacker to execute arbitrary code with the privileges of the Microsoft Office application, potentially leading to full system compromise. This could result in data theft, malware installation, or further lateral movement within the network. The vulnerability is classified as HIGH severity with a CVSS score of 8.4. While the number of victims is currently unknown, the widespread use of Microsoft Office makes this a critical vulnerability to address.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003ePatch CVE-2026-40363 by applying the latest Microsoft Office updates from the Microsoft Security Response Center (MSRC) advisory.\u003c/li\u003e\n\u003cli\u003eEnable Microsoft Defender for Office 365 with exploit protection enabled.\u003c/li\u003e\n\u003cli\u003eDeploy the Sigma rules in this brief to your SIEM to detect exploitation attempts.\u003c/li\u003e\n\u003cli\u003eMonitor process creation events for unusual child processes spawned by Microsoft Office applications.\u003c/li\u003e\n\u003cli\u003eTrain users to be cautious about opening unsolicited or suspicious documents, especially from unknown sources.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-05-12T18:35:23Z","date_published":"2026-05-12T18:35:23Z","id":"https://feed.craftedsignal.io/briefs/2026-05-cve-2026-40363-office-overflow/","summary":"A heap-based buffer overflow vulnerability in Microsoft Office allows an unauthenticated, local attacker to execute arbitrary code.","title":"CVE-2026-40363: Microsoft Office Heap-based Buffer Overflow","url":"https://feed.craftedsignal.io/briefs/2026-05-cve-2026-40363-office-overflow/"}],"language":"en","title":"CraftedSignal Threat Feed — Cve-2026-40363","version":"https://jsonfeed.org/version/1.1"}