CVE-2026-78518: microsoft 365_apps Out-of-bounds Read
CVSS: 8.8v3.1HighAnalyzed
Published 08-09-2026Last modified 14-10-2026
Vulnerability summary
CVE-2026-78518 is a high (CVSS 8.8) Out-of-bounds Read vulnerability in microsoft 365_apps. EPSS estimates a 0.86% chance of exploitation in the next 30 days, higher than 57.8% of scored vulnerabilities.
CVSS score
8.8/10
010
High · v3.1 (CVE.org)EPSS score
0.86%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Timeline
- 08-09-2026PublishedVulnerability first disclosed.
- 14-10-2026Last modifiedVulnerability information updated.
Description
Out-of-bounds read in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
CVSS metrics
2 scores · 2 sources · 1 versionHigh 8.8Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:CSourcesAll 2 agree
- NVDNIST8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.86%
Chance of exploitation in the next 30 days
Percentile
58%
Versus all other CVEs
30-day change
0.00 pp
From 0.86% on 20-09-2026
20-09-202620-10-2026
EPSS score0.86%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.
- CWE-20Improper Input ValidationThe product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
Affected systems
Microsoft16 products
- 365_appsna
- excel2016
- microsoft_365na
- microsoft 365 apps for enterprise≥ 16.0.1, < 16.0.20326.20138
- microsoft excel 2016≥ 16.0.0.0, < 16.0.5569.1003
1 vendor · 16 products
