CVE-2026-123377
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Heap-based Buffer Overflow in Microsoft Office Outlook

Vulnerability report for CVE-2026-123377, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.

Publication date: 2026-11-10

Last updated on: 2026-11-10

Assigner: Microsoft Corporation

Description

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

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published
2026-11-10
Last Modified
2026-11-10
Generated
2026-11-10
AI Q&A
2026-11-10
EPSS Evaluated
N/A
NVD
EUVD

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
Microsoft Microsoft Office LTSC 2021 From 16.0.1 (inc) to 16.0.14334.21048 (exc)
Microsoft Microsoft Office LTSC 2024 From 16.0.0 (inc) to 16.0.17932.21140 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-122 A 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().
CWE-190 The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.

Attack-Flow Graph

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Executive Summary

This is a heap-based buffer overflow vulnerability in Microsoft Office Outlook. It allows an unauthorized attacker to execute arbitrary code remotely over a network by exploiting a flaw in memory handling.

Impact Analysis

An attacker could exploit this to run malicious code on your system, potentially stealing data, installing malware, or taking control of your device. It requires user interaction like opening a specially crafted file.

Compliance Impact

This vulnerability could lead to unauthorized data access or exfiltration, violating GDPR (data protection) and HIPAA (health data privacy). Organizations must patch quickly to maintain compliance and avoid penalties.

Mitigation Strategies

Apply the latest security updates from Microsoft for Microsoft Office Outlook as soon as possible to patch the heap-based buffer overflow vulnerability.

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