Microsoft Office Excel: Remote code execution via use-after-free
Summary
A use-after-free memory flaw in Microsoft Office Excel allows an unauthorized attacker to execute code over a network. The attacker needs the victim to open a crafted file, for example an email attachment or a file from a shared drive or web link. Successful exploitation runs code with the rights of the user, so accounts with local admin rights carry higher risk.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 before the build listed at https://aka.ms/OfficeSecurityReleases
- Office 365 for Mac and Office LTSC for Mac 2021: before 16.115.26110837
- Office LTSC 2021: 16.0.1 before 16.0.14334.21048
- Office LTSC 2024: 16.0.0 before 16.0.17932.21140 (unverified, check MSRC)
- Office LTSC for Mac 2024: 16.0.0 before 16.115.26110837
- Office Online Server: 16.0.0.0 before 16.0.10417.20236 (unverified, check MSRC)
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (check the release notes at https://aka.ms/OfficeSecurityReleases)
- Office 365 for Mac and Office LTSC for Mac 2021: 16.115.26110837
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: 16.0.17932.21140 (unverified)
- Office Online Server: 16.0.10417.20236 (unverified)
Workaround
Unknown. No workaround is documented in the sources reviewed. Patching is the remedy.
- Until patched, keep Protected View enabled for files from the internet and email
- Block or quarantine unexpected .xls, .xlsx and .xlsm attachments
- Restrict macros (recommendation, not confirmed by Microsoft for this CVE)
Exploitation
- No evidence of exploitation in the wild as of the publication date
- Not listed in the CISA KEV catalog
- No public proof of concept known
- CISA SSVC: exploitation none, automatable no, technical impact total
Our recommendation
- Treat as high priority and deploy the November 2026 Office updates to all Excel-bearing clients, including Mac, within the normal cycle
- Prioritise users who handle external files and accounts with local admin rights
- Apply the hardening measures above until patched
- Re-check the MSRC page for confirmed build numbers, a possible SharePoint component, and exploitation updates
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Critical
- 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-2026-118730 msrc.microsoft.com
- CVE.org CVE Record CVE-2026-118730 www.cve.org
- Stefan Gossner: SharePoint security fixes November 2026 PU blog.stefan-gossner.com
- Cybersecuritynews: Microsoft November 2026 Patch Tuesday cybersecuritynews.com
- Strix AI: CVE-2026-118730 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, 21:41.
Original description (NVD)
Use after free 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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