CVE-2026-66810: microsoft 365_apps Heap-based Buffer Overflow

Vulnerability summary

CVE-2026-66810 is a medium (CVSS 5.5) Heap-based Buffer Overflow vulnerability in microsoft 365_apps. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 36.6% of scored vulnerabilities.

Timeline

1. 11-08-2026
   PublishedVulnerability first disclosed.
2. 21-10-2026
   Last modifiedVulnerability information updated.

Description

Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to disclose information locally.

• 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().