Microsoft Office Excel: Information disclosure through out-of-bounds read
Summary
Microsoft Office Excel contains an out-of-bounds read (CWE-125). An unauthorized attacker can disclose information over the network, for example memory contents, if a user opens a crafted spreadsheet. The CVSS 3.1 base score is 6.5 (Medium), the impact is limited to confidentiality, and Microsoft has published fixes.
Affected
- Microsoft 365 Apps for Enterprise: from 16.0.1, exact affected range per Microsoft advisory
- Office LTSC 2021: from 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: from 16.0.0 before 16.0.17932.21140
- Microsoft Office 365 for Mac and Office LTSC for Mac (2021 and 2024): before 16.115.26110837
- Office Online Server: before 16.0.10417.20236 (unverified, not listed in the CVE record)
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 Office LTSC for Mac: 16.115.26110837 or later
- Microsoft 365 Apps for Enterprise: fixed build unknown from the CVE record, see the MSRC advisory
- Office Online Server: unverified, see the MSRC advisory
Workaround
- Unknown. No workaround is documented in the sources reviewed.
- Until the update is installed, do not open untrusted Office attachments (own recommendation, not a vendor statement).
Exploitation
- No exploitation in the wild and no public proof of concept found in the sources reviewed. Not checked directly against the CISA KEV catalog or GitHub.
- CISA SSVC assessment: Exploitation none, Automatable no, Technical Impact partial.
Our recommendation
- Install the November 2026 Microsoft Office security updates for all Office variants, including Mac, through the normal patch cycle.
- Check the installed build against the fixed builds listed above, and confirm the Microsoft 365 Apps build in the MSRC advisory.
- Prioritize faster patching where Office is used to open untrusted attachments or downloads.
- Treat this as medium priority; other Excel vulnerabilities in the same release with remote code execution have higher priority.
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-2026-118300 msrc.microsoft.com
- CVE Record CVE-2026-118300 www.cve.org
- Microsoft 365 Apps security updates learn.microsoft.com
- Rapid7: Patch Tuesday November 2026 www.rapid7.com
- CVE-2026-118300 mirror (threatint) cve.threatint.com
- CVE-2026-118300 mirror (Strix) 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, 12:12.
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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