CVE-2026-62871: .NET Elevation of Privilege Vulnerability
CVE-2026-62871 is a remote code execution vulnerability in .NET, rated Important by Microsoft, with a CVSS 3.1 base score of 7.8 (High). An attacker can exploit it by an attacker with local access, without any privileges and only if a user takes an action. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 0.47% probability of exploitation activity in the next 30 days, higher than 41% of all scored vulnerabilities. Microsoft released the fix on 11 August 2026 in the August 2026 Patch Tuesday, delivered through 2 security updates (KB5122104, KB5122105). It affects 4 products in 1 product family (Developer Tools).
Key facts
- CVE ID
- CVE-2026-62871
- Severity
- High CVSS 7.8
- Microsoft severity
- Important
- Impact
- Remote Code Execution
- Exploited in the wild
- No
- Publicly disclosed
- No
- Exploitation likelihood
- Less Likely
- Weakness
- CWE-122; CWE-787
- EPSS
- 0.47% (percentile 41%)
- CISA KEV
- Not listed
- Released
- Last updated
- Patch Tuesday
- August 2026 Patch Tuesday
- Product families
- Developer Tools
CVSS score and vector
Microsoft scores CVE-2026-62871 at 7.8 (temporal 6.8) using CVSS 3.1. Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
| Metric | Value |
|---|---|
| Attack vector | Local |
| Attack complexity | Low |
| Privileges required | None |
| User interaction | Required |
| Scope | Unchanged |
| Confidentiality impact | High |
| Integrity impact | High |
| Availability impact | High |
| Exploit code maturity | Unproven |
| Remediation level | Official fix |
| Report confidence | Confirmed |
Description
Out-of-bounds write in .NET allows an unauthorized attacker to execute code locally.
Frequently asked questions (Microsoft)
What privileges could be gained by an attacker who successfully exploited this vulnerability?
An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.
According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?
Exploitation of this vulnerability requires that a user trigger the payload in the application.
Affected products (4)
Developer Tools
| Product | Security update | Type | Fixed build | Restart |
|---|---|---|---|---|
| .NET 8.0 runtime installed on Windows | KB5122104 | Security Update | 8.0.30 | Maybe |
| .NET 9.0 runtime installed on Windows | KB5122105 | Security Update | 9.0.19 | Maybe |
| Microsoft Visual Studio 2026 version 18.8 | Security update | Security Update | 18.8.3 | |
| Microsoft Visual Studio 2022 version 17.14 | Security update | Security Update | 17.14.38 |
Security updates (2)
NIST NVD data
Affected configurations (CPE)
| Product | Vulnerable versions |
|---|---|
| .net | from 8.0.0, before 8.0.30 |
| .net | from 9.0.0, before 9.0.19 |
| .net | from 10.0.0, before 10.0.11 |
| visual studio 2022 | from 17.14.0, before 17.14.38 |
| visual studio 2026 | from 18.8.0, before 18.8.3 |
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62871 (Patch, Vendor Advisory)
Acknowledgments
- 41ae55e9310ff27fa6f26af4727e5590
- kai63001
- Ky0toFu
- nono
Revision history
| Version | Date | Description |
|---|---|---|
| 1.0 | Information published. | |
| 2.0 | Removed Linux and macOS products from the Affected Software table. This is an informational change only. | |
| 2.1 | Updated an acknowledgement. This is an informational change only. |