Microsoft Office Click-to-Run: Local privilege escalation via use-after-free
Summary
Microsoft Office Click-to-Run, the delivery and update mechanism of Microsoft 365 Apps and Office LTSC 2021 and 2024, contains a use-after-free flaw (CWE-416). An attacker with local access and low privileges can exploit it to elevate privileges on the system. The attack complexity is high, so exploitation requires specific conditions. The flaw is local only and does not by itself allow remote access.
Affected
- Microsoft 365 Apps for Enterprise, 16.0.1 up to the fixed build (build number unknown, see Microsoft advisory)
- Microsoft Office LTSC 2021, 16.0.1 up to but excluding 16.0.14334.20974 (unverified)
- Microsoft Office LTSC 2024, 16.0.0 up to but excluding 16.0.17932.21056 (unverified)
Fixed in
- October 2026 Office security updates, released 13 October 2026
- Microsoft 365 Apps: Unknown.
- Office LTSC 2021: 16.0.14334.20974 or later (per third-party aggregators, not verified against MSRC)
- Office LTSC 2024: 16.0.17932.21056 or later (per third-party aggregators, not verified against MSRC)
Workaround
Unknown. No vendor workaround is documented. Installing the patch is the recommended fix.
Exploitation
- No known exploitation in the wild found.
- CISA SSVC: exploitation none, automatable no, technical impact total.
- Not listed in the CISA KEV catalogue (according to OpenCVE).
- No public proof of concept found.
Our recommendation
- Update Microsoft 365 Apps and Office LTSC via the normal Click-to-Run channel to the October 2026 security update or later.
- Check all Office installations, including terminal servers, for missing updates.
- Limit local administrator rights on workstations to reduce the impact of privilege escalation.
- Patch the complete October 2026 Office update together rather than this CVE alone.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-70276 msrc.microsoft.com
- Microsoft Office security release notes, October 2026 msrc.microsoft.com
- Microsoft Support KB index for Office updates support.microsoft.com
- OpenCVE: CVE-2026-70276 app.opencve.io
- Vulners: NVD record CVE-2026-70276 vulners.com
- Vulners: CVELIST record CVE-2026-70276 vulners.com
- Strix: CVE-2026-70276 www.strix.ai
- Vulners: EUVD-2026-100173 vulners.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 4 Nov 2026, 08:54.
Original description (NVD)
Use after free in Microsoft Office Click-To-Run allows an authorized attacker to elevate privileges locally.
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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