Microsoft Office Excel: Remote code execution via use-after-free
Summary
Microsoft Office Excel contains a use-after-free vulnerability (CWE-416). An unauthenticated attacker on the network can execute code on the affected system. Per the CVSS vector, a user must take an action, typically opening a crafted Excel file received by email or download. The CVSS base score is 8.8 (High).
Affected
- Microsoft 365 Apps for Enterprise: 16.0.1 up to the fixed build (build not stated in the source)
- Microsoft Office 365 for Mac: 1.0.0 to before 16.115.26110837
- Microsoft Office LTSC 2021: 16.0.1 to before 16.0.14334.21048
- Microsoft Office LTSC 2024: 16.0.0 to before 16.0.17932.21140
- Microsoft Office LTSC for Mac 2021: 16.0.1 to before 16.115.26110837
- Microsoft Office LTSC for Mac 2024: 16.0.0 to before 16.115.26110837
Fixed in
Unverified; the builds come from a third-party mirror of the CNA data and must be checked against the MSRC advisory:
- Microsoft Office LTSC 2021: 16.0.14334.21048 or later
- Microsoft Office LTSC 2024: 16.0.17932.21140 or later
- Office 365 for Mac and LTSC for Mac: 16.115.26110837 or later
- Microsoft 365 Apps for Enterprise: fixed build not stated; install the November 2026 Office security update
Workaround
Unknown. No vendor-documented workaround found. Patching is the remedy.
Exploitation
- Exploited in the wild: not found at the time of research.
- Public proof of concept: not found.
- Microsoft exploitability assessment: unknown.
Our recommendation
- Install the November 2026 Office security updates on all Microsoft 365, Office 2021/2024 and Mac installations, and verify the build number on each endpoint.
- Check whether Office updates are managed centrally and confirm the patch status.
- Keep Protected View enabled for files from the internet and restrict macros and attachments from untrusted senders.
- Instruct users not to open unexpected Excel files from unknown senders.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-124187 msrc.microsoft.com
- Strix mirror of CNA record CVE-2026-124187 www.strix.ai
- CyberSecurityNews: Microsoft November 2026 Patch Tuesday cybersecuritynews.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, 21:08.
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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