VDB-363207 · CVE-2026-40420 · EUVD-2026-29677

Microsoft Office 365 Apps/2019/LTSC 2021/LTSC 2024 access control

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	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.
8.1	$0-$5k	0.00

Summaryinfo

A vulnerability was found in Microsoft Office 365 Apps/2019/LTSC 2021/LTSC 2024. It has been classified as critical. This impacts an unknown function. Performing a manipulation results in access control. This vulnerability is reported as CVE-2026-40420. The attack requires a local approach. No exploit exists. It is recommended to apply a patch to fix this issue.

Detailsinfo

A vulnerability, which was classified as critical, was found in Microsoft Office 365 Apps/2019/LTSC 2021/LTSC 2024. This affects an unknown code block. The manipulation with an unknown input leads to a access control vulnerability. CWE is classifying the issue as CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Use after free in Microsoft Office allows an authorized attacker to elevate privileges locally.

The weakness was disclosed 05/12/2026 as confirmed security update guide (Website). It is possible to read the advisory at msrc.microsoft.com. This vulnerability is uniquely identified as CVE-2026-40420. The exploitability is told to be easy. Attacking locally is a requirement. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/04/2026). The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

Upgrading to version 28.1 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 EUVD (EUVD-2026-29677). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

Office Suite Software

Vendor

Microsoft

Name

Office

Version

License

commercial

Website

Vendor: https://www.microsoft.com/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.8
VulDB Meta Temp Score: 8.1

VulDB Base Score: 8.8
VulDB Temp Score: 7.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 8.8
Vendor Vector (Microsoft): 🔒

CNA Base Score: 8.8
CNA Vector (Microsoft): 🔒

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

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

Exploitinginfo

Class: Access control
CWE: CWE-284 / CWE-266
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Unproven

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Patch
Status: 🔍

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

Upgrade: Office 28.1

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-2026-40420 (🔒)
GCVE (CVE): GCVE-0-2026-40420
GCVE (VulDB): GCVE-100-363207
EUVD: 🔒

Entryinfo

Created: 05/12/2026 19:51
Updated: 06/04/2026 19:50
Changes: 05/12/2026 19:51 (27), 05/12/2026 19:52 (11), 05/12/2026 19:55 (32), 05/20/2026 09:57 (11), 06/03/2026 13:41 (1), 06/04/2026 19:50 (1)
Complete: 🔍
Cache ID: 216::103