Monivisor Top Full Crack May 2026

| # | Contribution | Section | |---|--------------|---------| | 1 | Discovery via fuzz‑testing of TOP handling | 2 | | 2 | Full exploit chain (guest → host RCE) | 3 | | 3 | Impact analysis across releases & configurations | 4 | | 4 | Mitigation strategies & vendor patch | 5 |

/* Fixed mask – only 48‑bit addresses allowed */
#define TOP_ADDR_MASK 0x0000FFFFFFFFFFFFULL
hmt_entry->addr = val & TOP_ADDR_MASK;

Additional hardening:

The full PoC (≈ 200 lines of C) is provided in Appendix A. It runs on a stock Monivisor 2.7 installation with default kernel parameters and requires only unprivileged guest user‑space code. monivisor top full crack

| Field | Size (bits) | Meaning | |-------|------------|---------| | TOP_ADDR | 48 | Guest‑provided physical address for mapping. | | TOP_FLAGS | 8 | Permission bits (RWX, cacheability). | | TOP_LEN | 8 | Length of the mapping (in pages). | | TOP_RESERVED | 0 | Must be zero. | Additional hardening: The full PoC (≈ 200 lines

The hyper‑visor implements top_set(uint64_t val) which extracts the fields, checks that TOP_ADDR falls within the guest‑visible physical range, and then writes an entry into the Host Mapping Table (HMT). addr = val & TOP_ADDR_MASK

Hyper‑visors are the cornerstone of modern cloud infrastructure. While much research has focused on classic vulnerabilities (e.g., VM‑exit handling, I/O emulation), register‑set interfaces have received comparatively little scrutiny. Monivisor’s design introduces a TOP (Target‑Operation‑Pointer) register, used by guests to request high‑performance memory mapping for zero‑copy I/O. The TOP register is intended to be write‑only from the guest perspective, with the hyper‑visor performing strict bounds checks before committing changes to host memory.