Microsoft Office Excel: Heap-based buffer overflow allows privilege escalation
Summary
A heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges over a network, according to the CVE record. The CVSS vector requires no privileges but user interaction (UI:R), so an attacker would typically need a user to open a crafted file, for example an email attachment or download. The CNA record lists Microsoft 365 Apps for Enterprise, Office for Mac, Office LTSC 2021/2024 and Office Online Server as affected. The CVSS score is 8.8 (High), and NVD had not yet completed its analysis at publication.
Affected
- Microsoft 365 Apps for Enterprise: from 16.0.1, before the build listed at aka.ms/OfficeSecurityReleases
- Office 365 for Mac: from 1.0.0, before 16.115.26110837
- Office LTSC 2021: from 16.0.1, before 16.0.14334.21048
- Office LTSC 2024: from 16.0.0, before 16.0.17932.21140 (unverified)
- Office LTSC for Mac 2021 and 2024: from 16.0.0 / 16.0.1, before 16.115.26110837 (unverified)
- Office Online Server: from 16.0.0.0, before 16.0.10417.20236 (unverified)
- Affected component to be confirmed against the MSRC advisory
Fixed in
- Office 365 for Mac: 16.115.26110837 or later
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later (unverified)
- Microsoft 365 Apps for Enterprise: Unknown. Build number not confirmed; see aka.ms/OfficeSecurityReleases
- Delivered in Microsoft's November 2026 update through Microsoft 365 / Office update channels
Workaround
Unknown. No vendor-documented workaround found. Applying the update is the priority.
Exploitation
- No evidence of exploitation in the wild found at publication
- No public proof-of-concept found
- Not listed in CISA KEV at last check
- CISA SSVC: exploitation none, automatable no, technical impact total
Our recommendation
- Deploy the November 2026 Microsoft 365 / Office updates to all affected Office installations, prioritising staff who open external files
- Verify installed build numbers against the fixed versions above
- Keep Protected View enabled for internet-sourced files and restrict macros and untrusted attachments as general hardening
- Re-check the MSRC advisory and NVD for confirmed build numbers and the affected component
Information from Microsoft (Patch Tuesday November 2026)
- Severity (Microsoft)
- Important
- Impact
- Elevation of privilege – 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
- CVE Record CVE-2026-118715 www.cve.org
- Microsoft Security Update Guide msrc.microsoft.com
- Strix.ai CVE-2026-118715 (version cross-check) www.strix.ai
- threatint CVE-2026-118715 (version cross-check) cve.threatint.com
- Stefan Gossner: SharePoint security fixes, November 2026 PU blog.stefan-gossner.com
- November 2026 Patch Tuesday summary (ntcompatible) www.ntcompatible.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, 21:46.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to elevate privileges 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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