What is CVE-2026-78505?
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code over a network.
The record classifies CVE-2026-78505 under weakness class CWE-122. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 8 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 52 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.8 — HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 4.4/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-09-08, last modified 2026-09-09
Is CVE-2026-78505 being exploited?
No public exploitation evidence for CVE-2026-78505 is recorded in the sources Threadlinqs tracks — CISA KEV, Exploit-DB, public proof-of-concept repositories and ProjectDiscovery Nuclei — as of 2026-09-09. That is an absence of evidence in those feeds, not a guarantee that the vulnerability is unexploited.
Affected products and versions
- Microsoft: 365 Apps for Enterprise, Office 2016, Office 2019, Office 365 for Mac, Office LTSC 2021, Office LTSC 2024, Office LTSC for Mac 2021, Office LTSC for Mac 2024
How to fix CVE-2026-78505
No vendor patch reference has been recorded for CVE-2026-78505 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-2026-78505
1 tracked threat in the Threadlinqs corpus references CVE-2026-78505, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, GitHub Security Advisories. Last verified by Threadlinqs on .