CVE-2026-70347: Windows Installer Elevation of Privilege Vulnerability

CSIRTS triage

What

A heap-based buffer overflow in Windows Installer permits an authorized attacker to elevate privileges locally.

Who is affected

Systems running Windows Installer with authorized users.

Urgency

High severity (CVSS 7.8); not currently exploited, but memory corruption flaws are often exploitable.

Action

Apply the latest Windows Update patches addressing CVE-2026-70347.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source

Microsoft Security Response Center (INTL · vendor-psirt · site)

Severity

high — CVSS 7.8

Published

2026-08-11

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-70347

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

• Low exploitation riskCVE-2026-703470.31% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 24% of all EPSS-scored CVEs.

Referenced CVEs

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

• unknownexploitedNCSC-2026-0284 [1.00] [M/H] Vulnerabilities patched in Microsoft Windowsncsc-nl
• highCVE-2026-70347: Heap-based buffer overflow in Windows Installer allows an authorized attacker to elevate privi…nvd

More from Microsoft Security Response Center

• highCVE-2026-70354: .NET Core Remote Code Execution Vulnerability2026-08-11
• highCVE-2026-68792: Microsoft Office Elevation of Privilege Vulnerability2026-08-11
• highCVE-2026-64909: Microsoft Office Remote Code Execution Vulnerability2026-08-11
• highCVE-2026-70130: Microsoft Office Remote Code Execution Vulnerability2026-08-11
• highCVE-2026-66807: Microsoft Office Graphics Component Remote Code Execution Vulnerability2026-08-11