CVE-2026-62886
High CVSS 7.8Published 2026-08-11 ยท last changed 2026-09-08
The fix
Microsoft fixes this in updatesKB5123099, KB5126043, KB5126421, KB5126424, KB5126052, KB5126422, KB5126046, KB5126048, KB5126050, KB5120747, KB5120716, KB5120695, KB5126044, KB5126045, KB5126053, KB5126047, KB5126049, KB5126051, KB5122106, KB5122104, KB5122105. The fixed build differs per Windows version, so the row that matters is the one matching the machine you are looking at.
| Windows version | Fixed in build | Update | Released |
|---|---|---|---|
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows 10 Version 1607 for 32-bit Systems | 2.0.50727.8984 & 3.0.30729.8980 & 4.7.4145.0 | KB5123099 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows 10 Version 1607 for x64-based Systems | 2.0.50727.8984 & 3.0.30729.8980 & 4.7.4145.0 | KB5123099 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2016 | 2.0.50727.8984 & 3.0.30729.8980 & 4.7.4145.0 | KB5123099 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2019 | 2.0.50727.9070 & 3.0.30729.9068 & 4.7.4145.0 | KB5126043 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for 32-bit Systems | 2.0.50727.9070 & 3.0.30729.9068 & 4.7.4145.0 | KB5126043 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for ARM64-based Systems | 2.0.50727.9070 & 3.0.30729.9068 & 4.7.4145.0 | KB5126043 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.7.2 on Windows 10 Version 1809 for x64-based Systems | 2.0.50727.9070 & 3.0.30729.9068 & 4.7.4145.0 | KB5126043 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 21H2 for 32-bit Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9346.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 21H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9346.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 21H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9346.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 22H2 for 32-bit Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9346.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 22H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9346.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 10 Version 22H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9346.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 23H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126424 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 23H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126424 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 24H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126052 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 24H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126052 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 25H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126052 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows 11 Version 25H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126052 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2022 | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126422 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8.1 on Windows Server 2025 | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.9347.0 | KB5126052 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for 32-bit Systems | 2.0.50727.9070 & 3.0.30729.9068 & 4.8.4806.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for ARM64-based Systems | 2.0.50727.9070 & 3.0.30729.9068 & 4.8.4806.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 1809 for x64-based Systems | 2.0.50727.9070 & 3.0.30729.9068 & 4.8.4806.0 | KB5126421 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 21H2 for 32-bit Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126046 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 21H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126046 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 21H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126046 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 22H2 for 32-bit Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126046 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 22H2 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126046 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows 10 Version 22H2 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126046 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2019 | 2.0.50727.9070 & 3.0.30729.9068 & 4.8.4806.0 | KB5126048 | 2026-09-20 |
| Microsoft .NET Framework 3.5 AND 4.8 on Windows Server 2022 | 2.0.50727.9183 & 3.0.30729.9169 & 4.8.4806.0 | KB5126050 | 2026-09-20 |
| Microsoft .NET Framework 3.5 on Windows 11 Version 26H1 for ARM64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 | KB5120747 | 2026-09-20 |
| Microsoft .NET Framework 3.5 on Windows 11 version 26H1 for x64-based Systems | 2.0.50727.9183 & 3.0.30729.9169 | KB5120747 | 2026-09-20 |
| Microsoft .NET Framework 3.5 on Windows Server 2012 | 2.0.50727.8984 & 3.0.30729.8980 | KB5120716 | 2026-09-20 |
| Microsoft .NET Framework 3.5 on Windows Server 2012 R2 | 3.0.50727.8984 | KB5120695 | 2026-09-20 |
| Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 | 4.7.4145.0 | KB5126044 | 2026-09-20 |
| Microsoft .NET Framework 4.6.2/4.7/4.7.1/4.7.2 on Windows Server 2012 R2 | 4.7.4145.0 | KB5126045 | 2026-09-20 |
| Microsoft .NET Framework 4.8.1 on Windows 11 Version 26H1 for ARM64-based Systems | 4.8.9347.0 | KB5126053 | 2026-09-20 |
| Microsoft .NET Framework 4.8.1 on Windows 11 version 26H1 for x64-based Systems | 4.8.9347.0 | KB5126053 | 2026-09-20 |
| Microsoft .NET Framework 4.8 on Windows 10 Version 1607 for 32-bit Systems | 4.8.4806.0 | KB5126047 | 2026-09-20 |
| Microsoft .NET Framework 4.8 on Windows 10 Version 1607 for x64-based Systems | 4.8.4806.0 | KB5126047 | 2026-09-20 |
| Microsoft .NET Framework 4.8 on Windows Server 2012 | 4.8.4806.0 | KB5126049 | 2026-09-20 |
| Microsoft .NET Framework 4.8 on Windows Server 2012 R2 | 4.8.4806.0 | KB5126051 | 2026-09-20 |
| Microsoft .NET Framework 4.8 on Windows Server 2016 | 4.8.4806.0 | KB5126047 | 2026-09-20 |
| .NET 10.0 installed on Windows | 10.0.11 | KB5122106 | 2026-09-20 |
| .NET 8.0 installed on Windows | 8.0.30 | KB5122104 | 2026-09-20 |
| .NET 9.0 installed on Windows | 9.0.19 | KB5122105 | 2026-09-20 |
Having the KB is not the same as knowing whether a machine has it. Windows updates supersede each other, so the update you installed often covers a fix that shipped in an earlier one. Paste your build into the patch checker and it walks that chain for you.
What it is
Integer overflow or wraparound in .NET allows an unauthorized attacker to elevate privileges locally.
Sources
CVSS vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H