Office Outlook: Remote code execution via stack-based buffer overflow
Summary
A stack-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network. The vulnerability is rated critical (CVSS 9.8). Per the research notes, a specially crafted email may trigger code execution through the Preview Pane without the recipient opening or clicking anything; no authentication is required.
Affected
- Microsoft 365 Apps for Enterprise (exact affected range: see MSRC advisory)
- Office LTSC 2021: 16.0.1 to before 16.0.14334.20974
- Office LTSC 2024: 16.0.0 to before 16.0.17932.21056
- Office 365 for Mac: before 16.114.26101123
- Office LTSC for Mac 2021: 16.0.1 to before 16.114.26101123
- Office LTSC for Mac 2024: 16.0.0 to before 16.114.26101123
Fixed in
- Microsoft 365 Apps for Enterprise: Unknown (see MSRC advisory)
- Office LTSC 2021: 16.0.14334.20974 or later (per third-party source, verify on MSRC)
- Office LTSC 2024: 16.0.17932.21056 or later (per third-party source, verify on MSRC)
- Office 365 for Mac and LTSC for Mac: Unknown
- Fixes were released in the October 2026 Patch Tuesday updates.
Workaround
- No vendor workaround found. Unknown.
- Interim measures (own recommendations, not from a vendor source): disable the Outlook Reading Pane and Preview Pane where feasible; ensure the mail gateway filters malicious attachments and content.
Exploitation
- Not known to be exploited in the wild. Not listed in the CISA KEV catalog.
- CISA SSVC: exploitation none; automatable: yes; technical impact: total.
- Rapid7 rates exploitation as less likely.
- No public proof-of-concept exploit found.
Our recommendation
- Patch Outlook and Office in the first wave, including Macs, and verify that Click-to-Run or update channels reached the fixed builds on all endpoints.
- Check the MSRC Security Update Guide for the current build numbers, especially for Microsoft 365 Apps and Mac.
- Patch the related October 2026 Outlook RCEs (CVE-2026-70242, CVE-2026-70291, CVE-2026-97016, CVE-2026-97749) together.
- Apply the interim measures above until patching is complete and monitor the MSRC page for updates.
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-2026-88156 msrc.microsoft.com
- OpenCVE: CVE-2026-88156 app.opencve.io
- CrowdStrike: Patch Tuesday analysis October 2026 www.crowdstrike.com
- Rapid7: Patch Tuesday October 2026 www.rapid7.com
- VulDB: CVE-2026-88156 vuldb.com
- Strix: CVE-2026-88156 www.strix.ai
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 30 Oct 2026, 18:24.
Original description (NVD)
Stack-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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