Microsoft Office Excel: Use after free leads to remote code execution
Summary
A use-after-free memory corruption flaw in Microsoft Excel, the spreadsheet component of Microsoft 365 Apps and Office LTSC editions, allows remote code execution. An attacker can run code on the victim's computer with the user's rights, with a CVSS score of 8.8 from the CNA. The attack requires no login, but a user must open a crafted file, typically one received by email or download. Nothing is known to be exploited yet, and no public proof of concept was found.
Affected
- Microsoft 365 Apps for Enterprise (16.0.1 up to the fixed build listed on the MSRC advisory)
- Microsoft Office 365 for Mac (1.0.0 before 16.115.26110837)
- Microsoft Office LTSC 2021 (16.0.1 before 16.0.14334.21048)
- Microsoft Office LTSC 2024 (affected; fixed version to be verified against MSRC, third-party aggregator gives 16.0.17932.21140)
- Office LTSC for Mac 2021 and 2024, Office Online Server: listed only by a secondary aggregator, unconfirmed
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (see MSRC advisory)
- Office 365 for Mac: 16.115.26110837
- Office LTSC 2021: 16.0.14334.21048
- Office LTSC 2024: Unknown from the CNA record; 16.0.17932.21140 per a third-party source, to be verified
- Office LTSC for Mac 2021 and 2024: unconfirmed, 16.115.26110837 per a third-party source
- Office Online Server: unconfirmed, 16.0.10417.20236 per a third-party source
Workaround
Unknown. No workaround documented by the vendor; patching is the fix.
Exploitation
- Not listed in CISA KEV at the time of research; no evidence of exploitation in the wild found.
- No public proof of concept found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- VulDB estimates exploitation as easy, but these are estimates, not confirmed activity.
Our recommendation
- Apply the Microsoft security update to all Microsoft 365 and Office LTSC clients in the normal patch cycle.
- Confirm installed builds against the MSRC table, since some fixed versions are unverified.
- Patch the related Excel memory-corruption CVEs from the same release (for example CVE-2026-118717 and CVE-2026-118719) together.
- Until patched, limit opening spreadsheets from untrusted email or downloads, and keep Office file-block and Protected View enabled.
- Check the CISA KEV catalogue again in the coming days.
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 msrc.microsoft.com
- CVE.org CVE Record www.cve.org
- VulDB CVE-2026-118716 vuldb.com
- Strix CVE-2026-118716 www.strix.ai
- CISA KEV alert 9 Nov 2026 www.cisa.gov
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, 21:46.
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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