What is CVE-2026-40366?
Use after free in Microsoft Office Word allows an unauthorized attacker to execute code locally.
The record classifies CVE-2026-40366 under weakness class CWE-416. Its CVSS v3 base vector states that the flaw requires local access to the host, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 7 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 169 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.4 — HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - EPSS (FIRST)
- 0.3% probability of exploitation in the next 30 days, higher than 28.2% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 5.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-05-12, last modified 2026-08-10
Is CVE-2026-40366 being exploited?
It currently carries a trending score of 12 in the Threadlinqs vulnerability feed.
Affected products and versions
- Microsoft: 365 Apps for Enterprise, Office 2019, Office LTSC 2021, Office LTSC 2024, Office LTSC for Mac 2021, Office LTSC for Mac 2024, Word 2016
How to fix CVE-2026-40366
No vendor patch reference has been recorded for CVE-2026-40366 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-40366
1 tracked threat in the Threadlinqs corpus references CVE-2026-40366, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, FIRST EPSS, GitHub Security Advisories. Last verified by Threadlinqs on .