Microsoft Office Excel: Out-of-bounds read leads to information disclosure
Summary
An out-of-bounds read in Microsoft Excel, part of several Microsoft Office releases, allows an unauthorized attacker to disclose information over a network. A user typically has to open a crafted spreadsheet, for example an email attachment or a download, before the flaw can be triggered. The CVSS vector rates only the confidentiality impact as high, so the flaw does not allow code execution. Microsoft has published fixes in its November 2026 updates.
Affected
- Microsoft 365 Apps for Enterprise: from 16.0.1, before a fixed build (exact build unknown, see vendor 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 (secondary source, not yet confirmed by Microsoft)
- Microsoft Office LTSC for Mac 2021 and 2024: before 16.115.26110837 (secondary source)
- Microsoft Office Online Server: from 16.0.0.0 before 16.0.10417.20236 (secondary source)
Fixed in
- Microsoft Office 365 for Mac: 16.115.26110837 or later
- Microsoft Office LTSC 2021: 16.0.14334.21048 or later
- Microsoft 365 Apps for Enterprise: Unknown, see the Microsoft advisory for the November 2026 update
- Microsoft Office LTSC 2024, LTSC for Mac and Office Online Server: see the fixed builds above, to be verified against the Microsoft Security Update Guide
Workaround
Unknown. Microsoft has not confirmed a workaround. Installing the November 2026 Office security updates is the recommended fix.
Exploitation
- No evidence of exploitation in the wild was found.
- Exploit code maturity is rated Unproven (E:U) in the CVSS vector.
- No public proof of concept and no CISA KEV entry were found.
- Rapid7 rates the flaw Exploitation Less Likely.
Our recommendation
- Install the November 2026 Microsoft Office security updates through your normal channel (Microsoft 365 update channel, WSUS/Intune or LTSC installer).
- Prioritise computers that regularly open external spreadsheets.
- Keep Protected View enabled and be cautious with spreadsheets from unknown senders until patched.
- Check the Microsoft Security Update Guide to confirm the fixed build for your product.
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Information disclosure – 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-2026-118727 msrc.microsoft.com
- CVE Record: CVE-2026-118727 www.cve.org
- Microsoft 365 Apps security updates learn.microsoft.com
- Rapid7: November 2026 Patch Tuesday analysis www.rapid7.com
- Strix: CVE-2026-118727 (secondary data) 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 11 Nov 2026, 12:11.
Original description (NVD)
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to disclose information 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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