Microsoft Windows up to Server 2025 SMB Client use after free

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.
6.4$5k-$25k0.00

Summaryinfo

A vulnerability described as critical has been identified in Microsoft Windows. This affects an unknown part of the component SMB Client. Such manipulation leads to use after free. This vulnerability is referenced as CVE-2026-40410. The attack can only be performed from a local environment. No exploit is available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Microsoft Windows and classified as critical. Affected by this issue is an unknown code block of the component SMB Client. The manipulation with an unknown input leads to a use after free vulnerability. Using CWE to declare the problem leads to CWE-416. Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Use after free in Windows SMB Client allows an authorized attacker to elevate privileges 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 handled as CVE-2026-40410. The exploitation is known to be difficult. The attack needs to be approached locally. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 05/19/2026).

Upgrading to version 10.0.17763.8755 eliminates this vulnerability. A possible mitigation has been published immediately after the disclosure of the vulnerability.

VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.0
VulDB Meta Temp Score: 6.4

VulDB Base Score: 7.0
VulDB Temp Score: 6.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 7.0
Vendor Vector (Microsoft): 🔒

CNA Base Score: 7.0
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: No

Availability: 🔒
Status: Unproven

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

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

Upgrade: Windows 10.0.17763.8755

Timelineinfo

05/12/2026 VulDB entry created
05/12/2026 +0 days Advisory disclosed
05/12/2026 +0 days Countermeasure disclosed
05/19/2026 +6 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-40410 (🔒)
GCVE (CVE): GCVE-0-2026-40410
GCVE (VulDB): GCVE-100-363200
scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 05/12/2026 19:47
Updated: 05/19/2026 05:08
Changes: 05/12/2026 19:47 (9), 05/12/2026 19:48 (28), 05/12/2026 19:51 (33), 05/19/2026 05:08 (11)
Complete: 🔍
Cache ID: 216::103

VulDB is the best source for vulnerability data and more expert information about this specific topic.

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