Microsoft · Memory corruption
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network
At a glance
~1% estimated chance of attack in 30 days. Exploitation not confirmed.
Low rather than Medium: UK relevance is 40 of 100, little UK-specific signal so far.
Briefing
- Do not treat uncorroborated claims as confirmed breaches.
Questions to ask IT
- Do we run Microsoft 365 Apps, Microsoft Office 2021 and Microsoft Office 2024, and which versions?
- If it is not yet patched, what mitigation is in place, and will the fix be done by 1 Dec?
Next steps
- Confirm whether this affects systems or suppliers in your estate
Vulnerability facts
Full CVE detail CVE-2026-70291- 9.8 · CriticalExploitable over the network without any account, and no one has to click or open anything. High impact on confidentiality, integrity and availability.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Not listed
- ~1.3% estimated chance of attack in 30 days
No technical write-up beyond these facts and the summary below yet.
Next steps
- Review the advisory against your asset inventory and patch cadence
Summary
- Microsoft is announcing the availability of the security updates for Microsoft Office for Mac. Customers running affected Mac software should install the update for their product to be protected from this vulnerability. Customers running other Microsoft Office software do not need to take any action. See the Release Notes for more information and download links.
- CVE-2026-70291 has an estimated ~1% chance of attack in 30 days (63th percentile) as of 2026-10-15 — probability signal, not confirmed exploitation
Read the original reportMicrosoft Security Update Guide RSS(opens in a new tab)
Products and services involved
- Microsoft 365 Apps93% match confidence · CVE-2026-70291
- Microsoft Office 202193% match confidence · CVE-2026-70291
- Microsoft Office 202493% match confidence · CVE-2026-70291
Pulse
Last checked 1 Nov · Recheck overdue since 2 Nov 2026, 03:37 UK time
held at 1.0%; ranking metadata was updated.
Sources
CVE-2026-70291 Microsoft Office Outlook Remote Code Execution Vulnerability
How we know
Statements extracted from sources. Higher confidence means stronger corroboration.
- ClaimedHeadline60% confidence
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorised attacker to execute code over a network
- ProbableSummary fact75% confidence
Microsoft is announcing the availability of the security updates for Microsoft Office for Mac. Customers running affected Mac software should install the update for their product to be protected from this vulnerability. Customers running other Microsoft Office software do not need to take any action. See the [Release Notes](https://go.microsoft.com/fwlink/p/?linkid=831049) for more information and download links.
- ConfirmedCVE identifier95% confidence
Event involves CVE-2026-70291
- ConfirmedEstimated attack likelihood95% confidence
CVE-2026-70291 has an estimated ~1% chance of attack in 30 days (63th percentile) as of 2026-10-15 — probability signal, not confirmed exploitation