Microsoft Word up to Word 2016 use after free

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
7.1$0-$5k0.00

Summaryinfo

A vulnerability was found in Microsoft Word up to Word 2016. It has been declared as critical. This issue affects some unknown processing. The manipulation results in use after free. This vulnerability is known as CVE-2026-40366. It is possible to launch the attack remotely. No exploit is available. It is advisable to implement a patch to correct this issue.

Detailsinfo

A vulnerability, which was classified as critical, was found in Microsoft Word up to Word 2016. Affected is some unknown processing. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

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

The weakness was published 05/12/2026 as confirmed security update guide (Website). The advisory is shared for download at msrc.microsoft.com. This vulnerability is traded as CVE-2026-40366. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 06/04/2026).

The vulnerability scanner Nessus provides a plugin with the ID 314343 (Security Updates for Microsoft Word Products (May 2026)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 16.0.5552.1002 eliminates this vulnerability. Applying a patch is able to eliminate this problem. The best possible mitigation is suggested to be patching the affected component. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (314343). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.7
VulDB Meta Temp Score: 7.1

VulDB Base Score: 6.3
VulDB Temp Score: 5.5
VulDB Vector: 🔒
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 8.4
Vendor Vector (Microsoft): 🔒

CNA Base Score: 8.4
CNA Vector (Microsoft): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Use after free
CWE: CWE-416 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: Yes

Availability: 🔒
Status: Unproven

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 314343
Nessus Name: Security Updates for Microsoft Word Products (May 2026)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔒
0-Day Time: 🔒
Exposure Time: 🔒

Upgrade: Word 16.0.5552.1002

Timelineinfo

05/12/2026 VulDB entry created
05/12/2026 +0 days Advisory disclosed
05/12/2026 +0 days Countermeasure disclosed
06/04/2026 +23 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-40366 (🔒)
GCVE (CVE): GCVE-0-2026-40366
GCVE (VulDB): GCVE-100-363180

Entryinfo

Created: 05/12/2026 19:39
Updated: 06/04/2026 18:27
Changes: 05/12/2026 19:39 (32), 05/12/2026 19:42 (37), 05/13/2026 14:58 (2), 05/20/2026 09:21 (12), 06/04/2026 18:27 (1)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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