CVE-2026-40403: Windows Graphics Component Remote Code Execution Vulnerability
CVE-2026-40403 is a remote code execution vulnerability in Windows Graphics Component, rated Critical by Microsoft, with a CVSS 3.1 base score of 8.8 (High). An attacker can exploit it by an attacker with local access, with low privileges and without user interaction. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 0.43% probability of exploitation activity in the next 30 days, higher than 37% of all scored vulnerabilities. Microsoft released the fix on 12 May 2026 in the May 2026 Patch Tuesday, delivered through 16 security updates (KB5087538, KB5087545, KB5087424, KB5087544 and more). It affects 31 products in 2 product families (Windows, ESU).
Key facts
- CVE ID
- CVE-2026-40403
- Severity
- High CVSS 8.8
- Microsoft severity
- Critical
- Impact
- Remote Code Execution
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- Weakness
- CWE-122
- EPSS
- 0.43% (percentile 37%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- May 2026 Patch Tuesday
- Product families
- Windows, ESU
CVSS score and vector
Microsoft scores CVE-2026-40403 at 8.8 (temporal 7.7) using CVSS 3.1. Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Local |
| Attack complexity | Low |
| Privileges required | Low |
| User interaction | None |
| Scope | Changed |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Heap-based buffer overflow in Windows Win32K - GRFX allows an authorized attacker to execute code locally.
Frequently asked questions (Microsoft)
According to the CVSS metric, a successful exploitation could lead to a scope change (S:C). What does this mean for this vulnerability?
This vulnerability could lead to a contained execution environment escape. Please refer to AppContainer Isolation for more information.
According to the CVSS metric, the attack vector is local (AV:L). Why does the CVE title indicate that this is a remote code execution?
The word Remote in the title refers to the location of the attacker. This type of exploit is sometimes referred to as Arbitrary Code Execution (ACE). The attack itself is carried out locally.
The vulnerable endpoint is only available over the local VM interface as all external communication is blocked. This means an attacker needs to execute code from the local machine to exploit the vulnerability.
According to the CVSS metric, privileges required is low (PR:L). What does that mean for this vulnerability?
Any authenticated attacker could trigger this vulnerability. It does not require admin or other elevated privileges.
How could an attacker exploit this vulnerability?
An attacker can exploit this vulnerability by getting access to the local guest VM so they can attack the Host OS.
Affected products (31)
Windows
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Windows 10 Version 1809 for 32-bit Systems | KB5087538 | Security Update | 10.0.17763.8755 | Yes |
| Windows 10 Version 1809 for x64-based Systems | KB5087538 | Security Update | 10.0.17763.8755 | Yes |
| Windows Server 2019 | KB5087538 | Security Update | 10.0.17763.8755 | Yes |
| Windows Server 2019 (Server Core installation) | KB5087538 | Security Update | 10.0.17763.8755 | Yes |
| Windows Server 2022 | KB5087545 KB5087424 | Security Update Security Hotpatch Update | 10.0.20348.5139 10.0.20348.5074 | Yes Yes |
| Windows Server 2022 (Server Core installation) | KB5087545 KB5087424 | Security Update Security Hotpatch Update | 10.0.20348.5139 10.0.20348.5074 | Yes Yes |
| Windows 10 Version 21H2 for 32-bit Systems | KB5087544 | Security Update | 10.0.19044.7291 | Yes |
| Windows 10 Version 21H2 for ARM64-based Systems | KB5087544 | Security Update | 10.0.19044.7291 | Yes |
| Windows 10 Version 21H2 for x64-based Systems | KB5087544 | Security Update | 10.0.19044.7291 | Yes |
| Windows Server 2025 (Server Core installation) | KB5087539 KB5087423 | Security Update Security Hotpatch Update | 10.0.26100.32860 10.0.26100.32772 | Yes Yes |
| Windows 11 Version 25H2 for ARM64-based Systems | KB5089549 KB5089466 | Security Update Security Hotpatch Update | 10.0.26200.8457 10.0.26200.8390 | Yes Yes |
| Windows 11 Version 25H2 for x64-based Systems | KB5089549 KB5089466 | Security Update Security Hotpatch Update | 10.0.26200.8457 10.0.26200.8390 | Yes Yes |
| Windows 11 Version 23H2 for ARM64-based Systems | KB5087420 | Security Update | 10.0.22631.7079 | Yes |
| Windows 11 Version 23H2 for x64-based Systems | KB5093998 | Security Update | 10.0.22631.7219 | Yes |
| Windows Server 2022, 23H2 Edition (Server Core installation) | KB5087541 | Security Update | 10.0.25398.2330 | Yes |
| Windows 11 Version 24H2 for ARM64-based Systems | ||||
| Windows 11 Version 24H2 for x64-based Systems | ||||
| Windows Server 2025 | KB5087539 KB5087423 | Security Update Security Hotpatch Update | 10.0.26100.32860 10.0.26100.32772 | Yes Yes |
| Windows 11 version 26H1 for x64-based Systems | KB5089548 | Security Update | 10.0.28000.2113 | Yes |
| Windows 11 Version 26H1 for ARM64-based Systems | KB5089548 | Security Update | 10.0.28000.2113 | Yes |
| Windows 10 Version 1607 for 32-bit Systems | KB5087537 | Security Update | 10.0.14393.9140 | Yes |
| Windows 10 Version 1607 for x64-based Systems | KB5087537 | Security Update | 10.0.14393.9140 | Yes |
| Windows Server 2016 | KB5087537 | Security Update | 10.0.14393.9140 | Yes |
| Windows Server 2016 (Server Core installation) | KB5087537 | Security Update | 10.0.14393.9140 | Yes |
ESU
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| Windows 10 Version 22H2 for x64-based Systems | KB5094127 | Security Update | 10.0.19045.7417 | Yes |
| Windows 10 Version 22H2 for ARM64-based Systems | KB5094127 | Security Update | 10.0.19045.7417 | Yes |
| Windows 10 Version 22H2 for 32-bit Systems | KB5094127 | Security Update | 10.0.19045.7417 | Yes |
| Windows Server 2012 | KB5087470 | Monthly Rollup | 6.2.9200.26079 | Yes |
| Windows Server 2012 (Server Core installation) | KB5087470 | Monthly Rollup | 6.2.9200.26079 | Yes |
| Windows Server 2012 R2 | KB5087471 | Monthly Rollup | 6.3.9600.23181 | Yes |
| Windows Server 2012 R2 (Server Core installation) | KB5087471 | Monthly Rollup | 6.3.9600.23181 | Yes |
Security updates (16)
- KB5087538 (Security Update)
- KB5087545 (Security Update)
- KB5087424 (Security Hotpatch Update)
- KB5087544 (Security Update)
- KB5094127 (Security Update)
- KB5087539 (Security Update)
- KB5087423 (Security Hotpatch Update)
- KB5089549 (Security Update)
- KB5089466 (Security Hotpatch Update)
- KB5087420 (Security Update)
- KB5093998 (Security Update)
- KB5087541 (Security Update)
- KB5089548 (Security Update)
- KB5087537 (Security Update)
- KB5087470 (Monthly Rollup)
- KB5087471 (Monthly Rollup)
NIST NVD data
- NVD status
- Analyzed
- NVD CVSS
- 8.8 (HIGH)
- NVD weakness
- CWE-122
- Published to NVD
- NVD last modified
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| windows 10 1607 (x64) | before 10.0.14393.9140 |
| windows 10 1607 (x86) | before 10.0.14393.9140 |
| windows 10 1809 (x64) | before 10.0.17763.8755 |
| windows 10 1809 (x86) | before 10.0.17763.8755 |
| windows 10 21h2 (arm64) | before 10.0.19044.7291 |
| windows 10 21h2 (x64) | before 10.0.19044.7291 |
| windows 10 21h2 (x86) | before 10.0.19044.7291 |
| windows 10 22h2 (arm64) | before 10.0.19045.7291 |
| windows 10 22h2 (x64) | before 10.0.19045.7291 |
| windows 10 22h2 (x86) | before 10.0.19045.7291 |
| windows 11 23h2 (arm64) | before 10.0.22631.7079 |
| windows 11 23h2 (x64) | before 10.0.22631.7079 |
| windows 11 24h2 (arm64) | before 10.0.26100.8390 |
| windows 11 24h2 (x64) | before 10.0.26100.8390 |
| windows 11 25h2 (arm64) | before 10.0.26200.8390 |
| windows 11 25h2 (x64) | before 10.0.26200.8390 |
| windows 11 26h1 (arm64) | before 10.0.28000.2113 |
| windows 11 26h1 (x64) | before 10.0.28000.2113 |
| windows server 2012 | all listed versions |
| windows server 2012 r2 | all listed versions |
| windows server 2016 | before 10.0.14393.9140 |
| windows server 2019 | before 10.0.17763.8755 |
| windows server 2022 | before 10.0.20348.5074 |
| windows server 2022 23h2 | before 10.0.25398.2330 |
| windows server 2025 | before 10.0.26100.32772 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40403 (Vendor Advisory)
Acknowledgments
- Calif.io and Milad Nasr (Anthropic) with Claude with Calif.io and Anthropic
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. |