Microsoft Office Excel: Remote code execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Office Excel allows an unauthenticated attacker to execute code over a network. User interaction is required, typically by opening a crafted Excel file received by email, download or shared drive. Successful exploitation runs code in the context of the user, with high impact on confidentiality, integrity and availability.
Affected
- Microsoft 365 Apps for Enterprise (16.0.1 up to the fixed build; exact fixed build not stated in the CNA record)
- Microsoft Office 365 for Mac: 1.0.0 to before 16.115.26110837
- Microsoft Office LTSC 2021: 16.0.1 to before 16.0.14334.21048
- Microsoft Office LTSC 2024: 16.0.0 to before 16.0.17932.21140
- Microsoft Office LTSC for Mac 2021: 16.0.1 to before 16.115.26110837
- Microsoft Office LTSC for Mac 2024: 16.0.0 to before 16.115.26110837 (to be confirmed on MSRC)
- Microsoft Office Online Server: 16.0.0.0 to before 16.0.10417.20236 (to be confirmed on MSRC)
Fixed in
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later
- Office 365 for Mac and LTSC for Mac 2021: 16.115.26110837 or later
- Microsoft 365 Apps for Enterprise and Office Online Server: Unknown (confirm on MSRC)
Workaround
Unknown. No vendor mitigation was confirmed in the sources. Patching is the primary fix.
Exploitation
Unknown. No evidence of exploitation in the wild, public proof of concept or CISA KEV listing was found at the time of research. NVD analysis is still pending.
Our recommendation
- Confirm the fixed builds for each product line on the MSRC advisory.
- Patch Microsoft 365 Apps and Office LTSC clients in the November 2026 update cycle with high priority.
- Until patched, restrict macros and external content and keep Protected View enabled for files from email and downloads.
- Warn users about unsolicited Excel attachments, since phishing is the main attack path.
- Monitor NVD and CISA KEV for changes in status.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Remote code execution – Microsoft Office Excel
- Status on Patch Tuesday
- Neither exploited nor publicly disclosed
- Exploitability assessment
- Exploitation less likely
- Product family
- Microsoft Office
- Updates (KB)
- KB5002946
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Response Center: CVE-2026-124176 msrc.microsoft.com
- Strix CVE mirror: CVE-2026-124176 (secondary, unverified) www.strix.ai
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, 21:08.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office Excel 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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