Microsoft Office Outlook: Heap-based buffer overflow enabling code execution
Summary
A heap-based buffer overflow in Microsoft Office Outlook (CVSS 8.8, CWE-122) allows an unauthorized attacker to execute code over the network. Exploitation requires the victim to interact, for example by opening a crafted message file. Microsoft's CNA record lists affected builds of Microsoft 365 Apps for Enterprise and Office LTSC 2021 and 2024, and the fix is part of the November 2026 Patch Tuesday.
Affected
- Microsoft 365 Apps for Enterprise: from 16.0.1, before the fixed build listed at https://aka.ms/OfficeSecurityReleases
- Office LTSC 2021: before 16.0.14334.21048
- Office LTSC 2024: before 16.0.17932.21140
Fixed in
- Microsoft 365 Apps for Enterprise: fixed build listed at https://aka.ms/OfficeSecurityReleases (exact build not confirmed)
- Office LTSC 2021: 16.0.14334.21048 or later
- Office LTSC 2024: 16.0.17932.21140 or later
- Patch: Microsoft November 2026 Patch Tuesday
Workaround
Unknown. No specific workaround or mitigation was found.
Exploitation
- Not marked as exploited in the wild in the Patch Tuesday coverage; treat as not known exploited until Microsoft says otherwise.
- No public proof of concept found.
- The exploited Outlook zero-day this month is CVE-2026-124194 (spoofing), a different CVE.
Our recommendation
- Update Microsoft 365 Apps and Office LTSC 2021/2024 to the November 2026 builds and verify the installed build against the advisory.
- Patch CVE-2026-124194 at the same time; it is exploited and listed in CISA KEV.
- Restrict or sandbox unsolicited message-file attachments at the mail gateway.
- Monitor NVD, the MSRC advisory and CISA KEV for changes.
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-2026-110043 msrc.microsoft.com
- CVE Record CVE-2026-110043 www.cve.org
- Microsoft November 2026 Patch Tuesday (Cybersecurity News) cybersecuritynews.com
- Microsoft Patch Tuesday November 2026 (CyberScoop) cyberscoop.com
- Exploited Outlook zero-day among 1094 flaws patched (SecurityWeek) www.securityweek.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, 23:50.
Original description (NVD)
Heap-based buffer overflow in Microsoft Office Outlook 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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