CVE-2026-42831: microsoft 365_copilot Heap-based Buffer Overflow

Vulnerability summary

CVE-2026-42831 is a high (CVSS 7.8) Heap-based Buffer Overflow vulnerability in microsoft 365_copilot. EPSS estimates a 0.47% chance of exploitation in the next 30 days, higher than 39% of scored vulnerabilities.

Timeline

1. 12-05-2026
   PublishedVulnerability first disclosed.
2. 10-08-2026
   Last modifiedVulnerability information updated.

Description

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code 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().