CVE-2026-45458: Microsoft Outlook and Word Remote Code Execution Vulnerability

highCVSS 8.4CVE-2026-45458

Access of resource using incompatible type ('type confusion') in Microsoft Office allows an unauthorized attacker to execute code locally.

CSIRTS triage

vendor: Microsoft product: Outlook Remote code execution

What: Access of resource using incompatible type ('type confusion') allows an unauthorized attacker to execute code locally.
Who is affected: Deployments of Microsoft Outlook.
Urgency: Remediation is urgent due to the high severity and potential for remote code execution.
Action: Apply the latest security patch for Microsoft Outlook.

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

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 8.4
Published: 2026-06-09
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45458

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-2026-454580.44% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 35% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-45458	coverage & exploitation status	NVD · CVE.org

Recent advisories for Microsoft Outlook and

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2025-59868: HCL Traveler for Microsoft Outlook (HTMO) is susceptible to a sensitive data exposure vulnerab…nvd · 2026-06-27
highCVE-2023-37524: HCL Traveler for Microsoft Outlook (HTMO) is susceptible to vulnerabilities due to .NET Framew…nvd · 2026-06-27
mediumCVE-2024-23581: The HCL Traveler for Microsoft Outlook libraries are being flagged as potentially malicious so…nvd · 2026-06-26
highCVE-2026-45456: Microsoft Outlook and Word Remote Code Execution Vulnerabilitymsrc · 2026-06-09
highCVE-2026-47635: Microsoft Outlook and Word Remote Code Execution Vulnerabilitymsrc · 2026-06-09
criticalexploitedCVE-2024-21413: Microsoft Outlook Improper Input Validation Vulnerabilitycisa-kev · 2025-02-06