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CVE-2026-21986 is an easily exploitable denial-of-service vulnerability in the Core component of Oracle VM VirtualBox affecting versions 7.1.14 and 7.2.4. The issue applies to Windows guest virtual machines. An unauthenticated attacker who has logon access to the infrastructure where VirtualBox executes can exploit the flaw to compromise VirtualBox availability. Oracle indicates that although the vulnerability resides in VirtualBox itself, exploitation may have scope change and significantly affect additional products. Successful exploitation results in a hang or a frequently repeatable crash of Oracle VM VirtualBox.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository is a small proof-of-concept exploit repo for CVE-2026-21986 affecting Oracle VM VirtualBox Shared Folders on Windows guests. It contains one executable code file, exploit/poc.cpp, plus supporting documentation in README.md and two markdown write-ups describing the root cause and memory exhaustion behavior. The exploit is a local denial-of-service PoC, not a remote exploit and not a framework module. The C++ program opens the VirtualBox Shared Folders device \\.\VBoxMiniRdrDN with CreateFileW, then repeatedly issues DeviceIoControl requests using IOCTL_MRX_VBOX_ADDCONN. For each request it builds a wide-character connection string based on the template \Device\VBoxMiniRdr\;X:\vboxsvr\sf, substitutes drive letters from Z through A, allocates a large user buffer with HeapAlloc, copies the connection string into the start of that buffer, and sends the oversized buffer to the driver. The code sets an additional padding size of 512 * 0x10000 bytes, roughly 32 MB beyond the base string length, and repeats this across 100 rounds to maximize kernel memory pressure. Its main capability is to induce repeated kernel non-paged pool allocations in the VBoxMiniRdr IOCTL handler until the guest becomes unstable or freezes. There is no shell, code execution, persistence, privilege escalation, beaconing, or data exfiltration functionality. The result is denial of service only. Repository structure is straightforward: README.md summarizes the vulnerability and impact; exploit/poc.cpp is the sole exploit implementation and likely entry point; writeup/technical_writeup.md explains the vulnerable device and exploitation flow; writeup/memory_analysis.md describes the allocation pattern and exhaustion mechanism. Overall, this is a credible, minimal PoC demonstrating local kernel memory exhaustion against an unpatched VirtualBox Shared Folders driver interface.
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