Microsoft Office: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Office allows an unauthorized remote attacker to execute code on the affected machine. The attack requires that a user opens or processes crafted content, for example a document received by email or downloaded from the internet. The CVSS base score is 8.8 (High), with full impact on confidentiality, integrity and availability of the local system. Microsoft reports no exploitation in the wild and no public proof-of-concept code at the time of writing.
Affected
- Microsoft 365 Apps for Enterprise from 16.0.1 (exact range end: see Microsoft advisory)
- Microsoft Office 365 for Mac from 1.0.0 before 16.115.26110837
- Microsoft Office LTSC 2021 from 16.0.1 before 16.0.14334.21048
- Microsoft Office LTSC 2024 from 16.0.0 before 16.0.17932.21140 (unconfirmed by CNA record)
- Microsoft Office LTSC for Mac 2021 from 16.0.1 before 16.115.26110837
- Microsoft Office LTSC for Mac 2024 from 16.0.0 before 16.115.26110837 (least certain, verify)
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown, see Microsoft Office security releases page (aka.ms/OfficeSecurityReleases)
- Office 365 for Mac: 16.115.26110837
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: 16.0.17932.21140 (per third-party trackers, verify with Microsoft)
- Office LTSC for Mac 2021 and 2024: 16.115.26110837 (per third-party trackers, verify with Microsoft)
Workaround
- Unknown. No vendor-published mitigation found; apply the security update.
- General practice: do not open attachments from unknown senders and keep Protected View enabled.
Exploitation
- Exploited in the wild: No evidence found.
- Public proof-of-concept: None found.
- CISA KEV status: Unknown.
- CISA SSVC: Exploitation none, automatable no, technical impact total.
Our recommendation
- Deploy the November 2026 Microsoft 365 and Office security updates on all Windows and Mac clients now.
- Confirm the exact fixed build for each channel in the Microsoft Security Update Guide and verify installed versions.
- Restrict opening documents from unknown senders and keep Protected View enabled until patched.
- Monitor for signs of exploitation and treat the whole November Office update as one deployment.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-120003 www.cve.org
- MSRC Security Update Guide advisory msrc.microsoft.com
- MSRC Security Update Guide msrc.microsoft.com
- Threatint mirror (version data) cve.threatint.com
- Strix CVE-2026-120003 www.strix.ai
- BleepingComputer Patch Tuesday coverage www.bleepingcomputer.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 10 Nov 2026, 21:33.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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