CVE-2026-70291: microsoft 365_apps Heap-based Buffer Overflow

Vulnerability summary

CVE-2026-70291 is a critical (CVSS 9.8) Heap-based Buffer Overflow vulnerability in microsoft 365_apps. EPSS estimates a 1.01% chance of exploitation in the next 30 days, higher than 62.5% of scored vulnerabilities.

Timeline

1. 13-10-2026
   PublishedVulnerability first disclosed.
2. 20-10-2026
   Last modifiedVulnerability information updated.

Description

Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

• 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().