CVE-2026-88145

Memory Safety in Microsoft Office 2021

Memory Safety

Published

13 October 2026

Modified

15 October 2026

Patch / advisory

View advisory

CVSS Score v3.1 8.8

Click a component to see what it means

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS Score 0.0072 53th percentile

Risk Priority 65 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-88145 is a high-severity Heap-based Buffer Overflow (CWE-122) vulnerability in Microsoft Office 2021. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Data Obfuscation (T1001); ranked in the top 47% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

EU & UK References

🇪🇺 ENISA EUVD: EUVD-2026-99726

Vulnerability Data

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

CWE(s): CWE-122 CWE-190

Related Threats

MITRE ATT&CK Enterprise Techniques

T1001 Data Obfuscation Command And Control

Adversaries may obfuscate command and control traffic to make it more difficult to detect.

attack.mitre.org →

T1001.002 Steganography Command And Control

Adversaries may use steganographic techniques to hide command and control traffic to make detection efforts more difficult.

attack.mitre.org →

T1003.001 LSASS Memory Credential Access

Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS).

attack.mitre.org →

T1003.004 LSA Secrets Credential Access

Adversaries with SYSTEM access to a host may attempt to access Local Security Authority (LSA) secrets, which can contain a variety of different credential materials, such as credentials for service accounts.

attack.mitre.org →

T1003.005 Cached Domain Credentials Credential Access

Adversaries may attempt to access cached domain credentials used to allow authentication to occur in the event a domain controller is unavailable.

attack.mitre.org →

T1003.006 DCSync Credential Access

Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API)(Citation: Microsoft DRSR Dec 2017) (Citation: Microsoft GetNCCChanges) (Citati…

attack.mitre.org →

Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

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CVE-2026-102856Same product: Microsoft 365 Apps

CVE-2026-64903Same product: Microsoft 365 Apps

CVE-2026-63532Same product: Microsoft 365 Apps

CVE-2026-55043Same product: Microsoft 365 Apps

Affected Assets

microsoft

365 apps

all versions

microsoft

microsoft 365

all versions

microsoft

office 2021

all versions

microsoft

office 2024

all versions

Mitigating Controls

Control response

Prevent

Stop it (NIST 800-53)

—

Detect

Catch it (NIST detect / respond)

—

Harden

Shrink the surface (DISA STIG)

—

Validate

Prove the fix (OWASP ASVS)

V1.4.1
V5.2.6

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation partial match

Developer testing and evaluation (including fuzzing and memory-error detectors) can discover heap overflows after they have been coded.

SA-8 Security and Privacy Engineering Principles partial match

Security engineering principles require use of memory-safe constructs and bounds-checked allocation routines that avoid introducing heap overflows.

SI-10 Information Input Validation partial match

Input validation enforces bounds checking on data written to heap buffers, directly stopping the overflow condition from being introduced.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

ID.RA-01 partial match

blocks

Vulnerability scanning and recording can discover heap-overflow flaws but does not prevent their introduction in code.

PR.PS-02 partial match

blocks

Timely patching removes known heap-overflow instances after they exist.

PR.PS-06 partial match

blocks

Secure-development practices directly require bounds checking and safe memory handling that prevent heap overflows.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match

removes

A.5.15 Access control partial match

removes

A.5.16 Identity management partial match

removes

A.5.17 Authentication information partial match

removes

A.5.18 Access rights partial match

removes

A.8.10 Information deletion partial match

removes