Microsoft Office Word: Heap-based buffer overflow allows remote code execution
Summary
A heap-based buffer overflow in Microsoft Office Word allows remote code execution. An attacker can run code in the context of the logged-on user by convincing a victim to open a crafted document, for example via a phishing email. No privileges are required, but user interaction is needed, and CISA's SSVC rates the technical impact as total.
Affected
- Microsoft 365 Apps for Enterprise (32- and 64-bit): 16.0.1 up to the fixed build (exact upper bound: see MSRC advisory)
- Office 365 for Mac: 1.0.0 to < 16.114.26101123
- Office LTSC 2021 (32- and 64-bit): 16.0.1 to < 16.0.14334.20974
- Office LTSC 2024 (32- and 64-bit): 16.0.0 to < 16.0.17932.21056
- Office LTSC for Mac 2021: 16.0.1 to < 16.114.26101123
- Office LTSC for Mac 2024: 16.0.0 to < 16.114.26101123
Fixed in
- Per-CVE fixed builds: Unknown (not confirmed; verify on the MSRC advisory)
- October 13, 2026 security-update builds per Microsoft release notes:
- Current Channel 2609: 20430.20182
- Monthly Enterprise Channel 2609: 20430.20180; 2608: 20326.20232; 2607: 20228.20276
- Semi-Annual Enterprise Channel 2609: 20430.20178; 2608: 20326.20230; 2607: 20228.20274
- LTSC 2024: 17932.21056; LTSC 2021: 14334.20974; LTSC 2019: 10417.20228
Workaround
Unknown. No vendor-documented workaround specific to this CVE was found.
- General interim measure (not CVE-specific): block or quarantine untrusted Word attachments at the mail gateway and restrict macro and document opening from untrusted sources.
Exploitation
- Not listed in CISA KEV
- CISA SSVC: exploitation none, not automatable
- CVSS temporal vector uses E:U (exploit code maturity: unproven)
- No public proof-of-concept found in the research
- EPSS values conflict between sources (0.00618 or unknown)
Our recommendation
- Deploy the October 13, 2026 Office security update to all affected channels and verify the build numbers against the MSRC advisory
- Inventory Office 2021 and LTSC 2021 installations; Office 2021 is out of support as of October 13, 2026, so plan a migration
- Keep mail gateway and attachment filtering for Word files in place until patching is verified
- Monitor CISA KEV and vendor advisories for changes in exploitation status
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-2026-70287 msrc.microsoft.com
- Microsoft 365 Apps security updates (release notes) learn.microsoft.com
- NVD entry via Vulners: CVE-2026-70287 vulners.com
- OpenCVE: CVE-2026-70287 app.opencve.io
- Office Watch: October 2026 Patch Tuesday Office fixes office-watch.com
- Qualys: Microsoft Patch Tuesday October 2026 review blog.qualys.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, 18:45.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office Word 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.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.