Microsoft Office Excel: Remote Code Execution via heap-based buffer overflow
Summary
A heap-based buffer overflow in Microsoft Excel allows an unauthorized attacker to execute code over a network. The CVSS 3.1 score is 8.8 (High), and the vector requires no privileges but user interaction, such as opening a malicious spreadsheet. Exposure is mainly through email attachments and shared files. No exploitation or public proof-of-concept code has been reported as of the research date.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (exact build not confirmed; see MSRC)
- Microsoft 365 for Mac (Office 365 for Mac): 1.0.0 to before 16.115.26110837
- Office LTSC 2021: 16.0.1 to before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 to before 16.0.17932.21140
- Office LTSC for Mac 2021: 16.0.1 to before 16.115.26110837
- Office LTSC for Mac 2024: 16.0.0 to before 16.115.26110837
- Office Online Server: 16.0.0.0 to before 16.0.10417.20236
Note: Third-party snapshots disagree on the Mac and Online Server entries. Verify on MSRC.
Fixed in
- Office LTSC 2021: 16.0.14334.21048 (per CNA record, to be confirmed)
- Office LTSC 2024: 16.0.17932.21140 (per CNA record, to be confirmed)
- Office for Mac and LTSC for Mac 2021/2024: 16.115.26110837 (per CNA record, to be confirmed)
- Office Online Server: 16.0.10417.20236 (per CNA record, to be confirmed)
- Microsoft 365 Apps for Enterprise: Unknown. See the MSRC release notes.
Workaround
No vendor-documented workaround is known.
- Until patched, keep Protected View enabled for files from email and the internet.
- Block or restrict Excel macros and legacy file formats where business allows.
Exploitation
- No evidence of active exploitation or public proof-of-concept code was found.
- CISA SSVC assessment: Exploitation none, Automatable no, Technical Impact total.
- Not listed in CISA KEV at the time of research.
Our recommendation
- Install the November 2026 Office security updates on all Microsoft 365 and Office LTSC clients, prioritizing mailboxes and finance workflows.
- Confirm the exact fixed build for each Office channel on the MSRC advisory.
- Warn staff not to open unexpected spreadsheets from email or downloads.
- Monitor for public proof-of-concept code or exploitation reports and reassess priority if they appear.
- Check CISA KEV and NVD once analysis is complete.
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 Update Guide: CVE-2026-119986 msrc.microsoft.com
- Strix: CVE-2026-119986 (CNA data mirror) www.strix.ai
- Cybersecurity News: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
- WARP2Search: Microsoft November 2026 Patch Tuesday www.warp2search.net
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, 21:35.
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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