CVE-2026-78449: Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution Vulnerability
Published Sep 8, 2026
·Updated
Use after free in Reliable Multicast Transport Driver (RMCAST) allows an unauthorized attacker to execute code over a network.
Other sources
Windows Reliable Multicast Transport Driver (RMCAST) Remote Code Execution Vulnerability
— Microsoft
Affected Software
54 affected componentsFixes available
Microsoft Windows 11=25H2
10.0.26200.9445
Microsoft Windows 10=22H2
10.0.19045.7725
Microsoft Windows Server 2012<6.2.9200.26349
6.2.9200.26349
Microsoft Windows Server 2012 R2<6.3.9600.23397
6.3.9600.23397
Microsoft Windows Server 2012 R2<6.3.9600.23397
6.3.9600.23397
Microsoft Windows Server 2016<10.0.14393.9512
10.0.14393.9512
Microsoft Windows Server 2012<6.2.9200.26349
6.2.9200.26349
Microsoft Windows 11=26H1
10.0.28000.2954
Microsoft Windows Server 2016<10.0.14393.9512
10.0.14393.9512
Microsoft Windows 10=1607
10.0.14393.9512
Microsoft Windows 10=1607
10.0.14393.9512
Microsoft Windows 11=24H2
10.0.26100.9445
Microsoft Windows 11=26H1
10.0.28000.2954
Microsoft Windows Server 2025<10.0.26100.33438
10.0.26100.33438
Microsoft Windows 11=24H2
10.0.26100.9445
Microsoft Windows 11=23H2
10.0.22631.7582
Microsoft Windows 11=23H2
10.0.22631.7582
Microsoft Windows 10=21H2
10.0.19044.7725
Microsoft Windows 11=25H2
10.0.26200.9445
Microsoft Windows Server 2022<10.0.20348.5622
10.0.20348.5622
Microsoft Windows 10=22H2
10.0.19045.7725
Microsoft Windows 10=21H2
10.0.19044.7725
Microsoft Windows Server 2025<10.0.26100.33438
10.0.26100.33438
Microsoft Windows 10=22H2
10.0.19045.7725
Microsoft Windows Server 2022<10.0.20348.5622
10.0.20348.5622
Microsoft Windows Server 2019<10.0.17763.9245
10.0.17763.9245
Microsoft Windows 10=21H2
10.0.19044.7725
Microsoft Windows 10=1809
10.0.17763.9245
Microsoft Windows 10=1809
10.0.17763.9245
Microsoft Windows Server 2019<10.0.17763.9245
10.0.17763.9245
Microsoft Windows 10 1607<10.0.14393.9512
Microsoft Windows 10 1607<10.0.14393.9512
Microsoft Windows 10 1809<10.0.17763.9245
Microsoft Windows 10 1809<10.0.17763.9245
Microsoft Windows 10 21h2<10.0.19044.7725
Microsoft Windows 10 21h2<10.0.19044.7725
Microsoft Windows 10 21h2<10.0.19044.7725
Microsoft Windows 10 22h2<10.0.19045.7725
Microsoft Windows 10 22h2<10.0.19045.7725
Microsoft Windows 10 22h2<10.0.19045.7725
Microsoft Windows 11 23h2<10.0.22631.7582
Microsoft Windows 11 23h2<10.0.22631.7582
Microsoft Windows 11 24h2<10.0.26100.9445
Microsoft Windows 11 24h2<10.0.26100.9445
Microsoft Windows 11 25h2<10.0.26200.9445
Microsoft Windows 11 25h2<10.0.26200.9445
Microsoft Windows 11 26h1<10.0.28000.2954
Microsoft Windows 11 26h1<10.0.28000.2954
Microsoft Windows Server 2012
Microsoft Windows Server 2012=r2
Microsoft Windows Server 2016<10.0.14393.9512
Microsoft Windows Server 2019<10.0.17763.9245
Microsoft Windows Server 2022<10.0.20348.5622
Microsoft Windows Server 2025<10.0.26100.33438
Remediation
Event History
Sep 8, 2026
CVE Published
via Microsoft·02:00 PM
Data Sourced
via Microsoft·02:00 PM
DescriptionSeverityWeakness
Data Sourced
via Microsoft·02:00 PM
Affected Software
Updated
via Microsoft·02:00 PM
Description
CVE Published
via MITRE·05:18 PM
Data Sourced
via MITRE·05:18 PM
DescriptionSeverity
Data Sourced
via NVD·06:20 PM
RemedyDescriptionSeverityWeaknessAffected Software
Frequently Asked Questions
1
What access does an attacker need to exploit this issue?
The vulnerability is remotely exploitable over a network and does not require attacker privileges or user interaction. Exploitation has high attack complexity.
2
Which systems should be prioritized for review?
Review Microsoft Windows 10, Windows 11, and the listed Windows Server releases: 2012, 2012 R2, 2016, 2019, 2022, and 2025. The available data does not identify affected build numbers, configurations, or update levels.
3
What is the potential impact of successful exploitation?
Successful exploitation can allow unauthorized remote code execution. The supplied severity data indicates high potential impact to confidentiality, integrity, and availability.