What is CVE-2026-77898?
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code over a network.
The record classifies CVE-2026-77898 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. 7 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 44 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 7.5 — HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C - EPSS (FIRST)
- 0.6% probability of exploitation in the next 30 days, higher than 47.5% of all scored CVEs
- CISA KEV
- Not listed in the CISA Known Exploited Vulnerabilities catalog
- Threadlinqs priority
- 5.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- Published
- 2026-09-08, last modified 2026-10-08
Is CVE-2026-77898 being exploited?
It currently carries a trending score of 39 in the Threadlinqs vulnerability feed.
Affected products and versions
- Microsoft: 365 Apps for Enterprise, 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-2026-77898
No vendor patch reference has been recorded for CVE-2026-77898 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-2026-77898
1 tracked threat in the Threadlinqs corpus references CVE-2026-77898, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on .