CVE-2025-26671
High CVSS 8.1Published 2025-04-08 ยท last changed 2026-06-17
The fix
Microsoft fixes this in updatesKB5055561, KB5055570, KB5055581, KB5055557, KB5055521, KB5055519, KB5055526, KB5055527, KB5055523. 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 |
|---|---|---|---|
| Windows Server 2008 R2 for x64-based Systems Service Pack 1 | 6.1.7601.27670 | KB5055561, KB5055570 | 2026-09-17 |
| Windows Server 2008 R2 for x64-based Systems Service Pack 1 (Server Core installation) | 6.1.7601.27670 | KB5055561, KB5055570 | 2026-09-17 |
| Windows Server 2012 | 6.2.9200.25423 | KB5055581 | 2026-09-17 |
| Windows Server 2012 R2 | 6.3.9600.22523 | KB5055557 | 2026-09-17 |
| Windows Server 2012 R2 (Server Core installation) | 6.3.9600.22523 | KB5055557 | 2026-09-17 |
| Windows Server 2012 (Server Core installation) | 6.2.9200.25423 | KB5055581 | 2026-09-17 |
| Windows Server 2016 | 10.0.14393.7969 | KB5055521 | 2026-09-17 |
| Windows Server 2016 (Server Core installation) | 10.0.14393.7969 | KB5055521 | 2026-09-17 |
| Windows Server 2019 | 10.0.17763.7136 | KB5055519 | 2026-09-17 |
| Windows Server 2019 (Server Core installation) | 10.0.17763.7136 | KB5055519 | 2026-09-17 |
| Windows Server 2022 | 10.0.20348.3453 | KB5055526 | 2026-09-17 |
| Windows Server 2022, 23H2 Edition (Server Core installation) | 10.0.25398.1551 | KB5055527 | 2026-09-17 |
| Windows Server 2022 (Server Core installation) | 10.0.20348.3453 | KB5055526 | 2026-09-17 |
| Windows Server 2025 | 10.0.26100.3775 | KB5055523 | 2026-09-17 |
| Windows Server 2025 (Server Core installation) | 10.0.26100.3775 | KB5055523 | 2026-09-17 |
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
Use after free in Windows Remote Desktop Services allows an unauthorized attacker to execute code over a network.
Sources
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H