Listen to this Post
CVE-2026-62816 is a critical heap-based buffer overflow vulnerability identified in the Microsoft Windows Reliable Multicast Transport Driver (RMCAST). The RMCAST driver is a Windows kernel component that enables reliable multicast communication over UDP, commonly used in enterprise environments for high-performance one-to-many data distribution such as financial market data feeds and live media streaming. The vulnerability stems from improper bounds checking when the driver processes specially crafted multicast packets, allowing an unauthorized attacker on an adjacent network to trigger a heap overflow condition. This overflow corrupts heap metadata and can be leveraged to achieve arbitrary code execution with kernel-level privileges.
The vulnerability is particularly dangerous because it requires no authentication and no user interaction. An attacker only needs network access to a system with the RMCAST driver active and a program listening on a Pragmatic General Multicast (PGM) port. If PGM is installed or enabled but no programs are actively listening as receivers, the vulnerability is not exploitable. PGM does not authenticate requests, so any system with an open PGM port is exposed.
Microsoft has assigned a CVSS 3.1 base score of 8.8 (HIGH) with the vector AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. The attack vector is adjacent network, attack complexity is low, privileges required are none, and user interaction is none. The scope is unchanged with high impacts on confidentiality, integrity, and availability. The vulnerability is classified under CWE-122 (Heap-based Buffer Overflow) and CWE-190 (Integer Overflow or Wraparound). Affected configurations include Windows 10 versions 1607 and 1809, among others. Microsoft has released an advisory and is expected to provide a patch through the August 2026 Patch Tuesday cycle.
DailyCVE Form:
Platform: ……. Windows 10, Server
Version: …….. 1607, 1809, others
Vulnerability :…… Heap Buffer Overflow
Severity: ……. 8.8 HIGH
date: ………. 08/11/2026
Prediction: …… August 2026 Patch Tuesday
What Undercode Say:
Analytics indicate active reconnaissance targeting PGM-enabled systems in enterprise environments. The following commands can be used to check RMCAST driver status and PGM listener activity:
Check if RMCAST driver is loaded
sc query rmcast
Check for PGM listeners on the system
netstat -ano | findstr :PGM
Get-NetUDPEndpoint | Where-Object { $_.LocalPort -eq 0 }
Check Windows version and build for CVE-2026-62816 affected range
systeminfo | findstr "OS Name" & systeminfo | findstr "OS Version"
Exploit: (Educational Purposes!)
The heap overflow is triggered by sending a malformed multicast packet to a PGM listening port on the target system. The crafted packet contains an oversized or malformed header field that exceeds the allocated heap buffer size in the RMCAST driver’s parsing routine. When the driver copies the packet data into the heap buffer without proper length validation, adjacent heap memory is overwritten, corrupting critical heap structures. A sophisticated attacker can craft the overflow to overwrite a function pointer or object vtable, redirecting execution flow to attacker-controlled shellcode embedded within the packet payload. This results in arbitrary code execution at kernel privilege level (SYSTEM). Proof-of-concept code typically involves raw socket programming to construct and transmit the malicious PGM packet over the adjacent network segment.
Protection:
- Apply Microsoft’s official security update as soon as it is released through Windows Update or the Microsoft Update Catalog.
- Block PGM traffic at the network perimeter and host firewall unless explicitly required.
- Disable the RMCAST driver if not in use: `sc config rmcast start= disabled` and reboot.
- Monitor for unusual multicast traffic patterns and unauthorized PGM connection attempts.
- Restrict adjacent network access to trusted systems only.
Impact:
Successful exploitation allows an unauthenticated attacker to execute arbitrary code with kernel-level privileges on the target system. This leads to complete system compromise, including unauthorized data access, data modification, denial of service, and potential lateral movement within the network. Enterprise environments using PGM for financial data distribution, live streaming, or other multicast services are at highest risk. The vulnerability requires no user interaction, making it highly attractive for automated worm-style propagation across adjacent network segments.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
Undercode
