Microsoft · Memory corruption
Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to disclose information locally
At a glance
Low rather than Medium: UK relevance is 40 of 100, little UK-specific signal so far.
Briefing
There is no written leader briefing for this story yet. These questions come from the facts we hold.
Questions to ask IT
- Do we run Microsoft 365 Apps, Microsoft Office 2019, Microsoft Office 2021 and 1 more, and which versions?
- If it is not yet patched, what mitigation is in place, and will the fix be done by 10 Dec?
Next steps
- Confirm whether this affects systems or suppliers in your estate
Vulnerability facts
Full CVE detail CVE-2026-66810- 5.5 · MediumExploitable only with local access without any account, but only if a user takes an action, such as opening a file or link. High impact on confidentiality.CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- Not listed
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
- Updated an acknowledgement. This is an informational change only.
Read the original reportMicrosoft Security Update Guide RSS(opens in a new tab)
Products and services involved
- Microsoft 365 Apps93% match confidence · CVE-2026-66810
- Microsoft Office 201993% match confidence · CVE-2026-66810
- Microsoft Office 202193% match confidence · CVE-2026-66810
- Microsoft Office 202493% match confidence · CVE-2026-66810
Part of Out-of-bounds read in Microsoft Office Word allows an unauthorized attacker to disclose information over a network
- Out-of-bounds read in Microsoft Office Word allows an unauthorized attacker to disclose information over a network
- Stack-based buffer overflow in Microsoft Graphics Component allows an authorized attacker to elevate privileges locally
- Missing authorization in Microsoft Office SharePoint allows an authorized attacker to execute code over a network
- Missing authorization in Microsoft Windows Search Component allows an authorized attacker to perform tampering locally
Pulse
Last change 46m ago · Next recheck 11 Nov 2026, 22:09 UK time
- Story10 Nov 2026, 22:09 UK time · 46m ago
Linked reporting from Microsoft Security Update Guide RSS (vendor psirt).
Read source (Microsoft Security Update Guide RSS)
1 entry so far. The timeline chart appears once this story has more history.
Sources
CVE-2026-66810 Microsoft Office Word Information Disclosure Vulnerability
How we know
Statements extracted from sources. Higher confidence means stronger corroboration.
- ClaimedHeadline60% confidence
Heap-based buffer overflow in Microsoft Office Word allows an unauthorised attacker to disclose information locally
- ProbableSummary fact75% confidence
Updated an acknowledgement. This is an informational change only.
- ConfirmedCVE identifier95% confidence
Event involves CVE-2026-66810