xooxo/cve-2026-35250Proof-of-concept for CVE-2026-35250, an integer overflow in VirtualBox's DevVGA_VBVA leading to denial of service via a privileged guest. Includes AI-assisted analysis and exploit module.
my firstever cve is a 2.3
Problem is at src/VBox/Devices/Graphics/DevVGA_VBVA.cpp:740-743 ASSERT_GUEST_MSG_RETURN where dimensions check uses || (OR) instead of && (AND). A guest can supply width=0x80000001, height=16 and the check passes because height <= 2048. Then on lines 745-746:
cbPointerData = ((((SafeShape.u32Width + 7) / 8) * SafeShape.u32Height + 3) & ~3)
+ SafeShape.u32Width * 4 * SafeShape.u32Height;
The subsequent check at line 748 (cbPointerData <= cbShape - 24) passes with the truncated value (80 <= 104). The host allocates 80 bytes via RTMemAlloc, copies 80 bytes from guest VRAM, then passes dimensions 2,147,483,649 × 16 with an 80-byte buffer to , which processes the cursor shape using the huge dimensions.
pfnVBVAMousePointerShapehost is computing AND mask scanline width from the overflowed dimensions and reading past the 80-byte heap buffer.
Crash 1 — NULL pointer WRITE (GUI display thread):
ExceptionCode=0xc0000005 ExceptionAddress=VirtualBoxVM.dll+0x000267a2
ExceptionInformation[0]=1 (WRITE) ExceptionInformation[1]=0x0000000000000000 (NULL)
rsi=0x80000001 (POISON_WIDTH) r13=0x10 (POISON_HEIGHT=16) rcx=0x0 (NULL dest)
Crash 2 — Heap over-READ (EMT/main thread):
ExceptionCode=0xc0000005 ExceptionAddress=VBoxC.dll+0x000d1194
ExceptionInformation[0]=0 (READ) ExceptionInformation[1]=0x00000263cefe8fd0
rax=0x80000001 (POISON_WIDTH) r12=0x10000001 ((WIDTH+7)/8 = AND scanline width)
r13=0x10 (POISON_HEIGHT=16) r8=0x80000001 (POISON_WIDTH)
Since host is 64-bit, I don't think it is an exploitable issue. For "exploit", do this on guest:
# Guest: build and load
cd /path/to/poc
make
sudo insmod gfx1_exploit.ko