Microsoft Office Excel: Use after free leads to remote code execution
Summary
Microsoft Office Excel contains a use-after-free memory corruption flaw (CWE-416). If a user opens a specially crafted Excel file, for example from an email or a download, an unauthorized attacker may be able to execute code in the context of the signed-in user. No authentication is required, but user interaction is. Microsoft released security updates on 10 November 2026.
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (exact build unknown)
- Office 365 for Mac: 1.0.0 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 (from an aggregator, unverified)
- Office LTSC for Mac 2021 and 2024: before 16.115.26110837
- Office Online Server: 16.0.0.0 before 16.0.10417.20236 (unverified, may not be covered by this CVE)
Fixed in
- Security update released on 10 November 2026 for 32-bit and 64-bit editions of Office LTSC 2021, Office LTSC 2024 and Microsoft 365 Apps for Enterprise
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later (unverified)
- Office for Mac: 16.115.26110837 or later
- Microsoft 365 Apps: build number unknown, check the MSRC page
Workaround
Unknown.
- No vendor workaround found. Patching is available.
- Interim measures until patched: restrict or block email and download attachments of Office files from untrusted senders, keep Protected View and Application Guard enabled, and block macros from the internet.
Exploitation
- No evidence of exploitation in the wild or public proof-of-concept code was found.
- The CVSS vector uses E:U (exploit maturity unproven).
- Strix lists KEV: No.
- MSRC exploitation flags for this CVE could not be retrieved, so confidence is low to moderate.
Our recommendation
- Treat as high priority for Microsoft 365 and LTSC clients.
- Deploy the November 2026 Office update across the whole suite and confirm build numbers against the MSRC page before rollout.
- Block or quarantine Office attachments from untrusted senders and keep Protected View enabled.
- Monitor for unusual Excel process activity on workstations.
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-2026-118713) msrc.microsoft.com
- CVE.org record CVE-2026-118713 www.cve.org
- Microsoft November 2026 Patch Tuesday (cybersecuritynews) cybersecuritynews.com
- Strix CVE-2026-118713 www.strix.ai
- threatint CVE-2026-118713 cve.threatint.com
- VulDB 434123 vuldb.com
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, 21:54.
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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.