CVE-2026-40364: microsoft 365_apps Heap-based Buffer Overflow
CVSS: 8.4v3.1HighAnalyzed
Published 12-05-2026Last modified 10-08-2026
Vulnerability summary
CVE-2026-40364 is a high (CVSS 8.4) Heap-based Buffer Overflow vulnerability in microsoft 365_apps. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 29% of scored vulnerabilities.
CVSS score
8.4/10
010
High · v3.1 (CVE.org)EPSS score
0.36%
0%100%
Low · -4.06 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 12-05-2026PublishedVulnerability first disclosed.
- 10-08-2026Last modifiedVulnerability information updated.
Description
Access of resource using incompatible type ('type confusion') in Microsoft Office Word allows an unauthorized attacker to execute code locally.
CVSS metrics
2 scores · 2 sources · 1 versionHigh 8.4Preferred score · CVE.org (CNA)
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CSourcesAll 2 agree
- NVDNIST8.4HighCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.36%
Chance of exploitation in the next 30 days
Percentile
29%
Versus all other CVEs
30-day change
-4.06 pp
From 4.42% on 21-09-2026
21-09-202621-10-2026
EPSS score0.36%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-122Heap-based Buffer OverflowA heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().
- CWE-843Access of Resource Using Incompatible Type ('Type Confusion')The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.
- CWE-908Use of Uninitialized ResourceThe product uses or accesses a resource that has not been initialized.
Affected systems
Microsoft11 products
- 365_appsna
- microsoft 365 apps for enterprise≥ 16.0.1, < https://aka.ms/OfficeSecurityReleases
- microsoft office 2019≥ 19.0.0, < https://aka.ms/OfficeSecurityReleases
- microsoft office ltsc 2021≥ 16.0.1, < https://aka.ms/OfficeSecurityReleases
- microsoft office ltsc 2024≥ 16.0.0, < https://aka.ms/OfficeSecurityReleases
1 vendor · 11 products
