Microsoft Office Excel: Remote code execution via integer underflow
Summary
Microsoft Office Excel contains an integer underflow (CWE-191) that allows remote code execution. According to the CVSS vector, an unauthenticated attacker can exploit it over the network, but a user must interact with the crafted content, for example by opening a file. A successful attack could affect confidentiality, integrity and availability. Exploitation is not known and no public proof of concept was found.
Affected
- Microsoft 365 Apps for Enterprise (16.0.1 up to the fixed build)
- Office LTSC 2021 and LTSC 2024 (Windows)
- Office 365 for Mac and LTSC for Mac 2021 and 2024
- Office Online Server (16.0.0.0 up to the fixed build)
Fixed in
Unknown. Check the MSRC advisory for the patched build per product and update channel. Third-party sources list 16.0.14334.20974 (LTSC 2021), 16.0.17932.21056 (LTSC 2024) and 16.0.10417.20228 (Office Online Server), but these values are not verified against Microsoft.
Workaround
Unknown. No vendor-documented workaround was found. Installing the Microsoft security update is the stated remedy.
Exploitation
- Not known to be exploited in the wild
- CISA SSVC assessment: exploitation none, automatable no
- Not listed in CISA KEV
- No public proof of concept found in a limited search
Our recommendation
- Install the Microsoft Office security update for all affected products and channels as a priority
- Verify the patched build numbers on the MSRC advisory before rollout
- Check whether Office Online Server is installed and reachable from the internet, and restrict or patch it first if so
- Keep Protected View enabled and restrict macros and files from untrusted sources
- Monitor for unusual Excel activity and re-check exploitation status regularly
Information from Microsoft (Patch Tuesday October 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)
- KB5002928
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- MSRC advisory CVE-2026-97746 msrc.microsoft.com
- Microsoft 365 Apps security updates (release notes) learn.microsoft.com
- KB5002928 Office Online Server support.microsoft.com
- OpenCVE (NVD and CISA SSVC data) app.opencve.io
- Vulners CNA version data vulners.com
- Strix third-party version table www.strix.ai
- GitHub alert tracker github.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 31 Oct 2026, 17:43.
Original description (NVD)
Integer underflow (wrap or wraparound) 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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