In the Linux kernel, the following vulnerability has been resolved:
x86/vmware: Fix hypercall clobbers
Fedora QA reported the following panic:
BUG: unable to handle page fault for address: 0000000040003e54 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20251119-3.fc43 11/19/2025 RIP: 0010:vmware_hypercall4.constprop.0+0x52/0x90 .. Call Trace: vmmouse_report_events+0x13e/0x1b0 psmouse_handle_byte+0x15/0x60 ps2_interrupt+0x8a/0xd0 ...
because the QEMU VMware mouse emulation is buggy, and clears the top 32 bits of %rdi that the kernel kept a pointer in.
The QEMU vmmouse driver saves and restores the register state in a "uint32_t data[6];" and as a result restores the state with the high bits all cleared.
RDI originally contained the value of a valid kernel stack address (0xff5eeb3240003e54). After the vmware hypercall it now contains 0x40003e54, and we get a page fault as a result when it is dereferenced.
The proper fix would be in QEMU, but this works around the issue in the kernel to keep old setups working, when old kernels had not happened to keep any state in %rdi over the hypercall.
In theory this same issue exists for all the hypercalls in the vmmouse driver; in practice it has only been seen with vmware_hypercall3() and vmware_hypercall4(). For now, just mark RDI/RSI as clobbered for those two calls. This should have a minimal effect on code generation overall as it should be rare for the compiler to want to make RDI/RSI live across hypercalls.
| Software | From | Fixed in |
|---|---|---|
| linux / linux_kernel | 6.11 | 6.12.70 |
| linux / linux_kernel | 6.13 | 6.18.10 |
| linux / linux_kernel | 6.19-rc1 | 6.19-rc1.x |
| linux / linux_kernel | 6.19-rc2 | 6.19-rc2.x |
| linux / linux_kernel | 6.19-rc3 | 6.19-rc3.x |
| linux / linux_kernel | 6.19-rc4 | 6.19-rc4.x |
| linux / linux_kernel | 6.19-rc5 | 6.19-rc5.x |
| linux / linux_kernel | 6.19-rc6 | 6.19-rc6.x |
| linux / linux_kernel | 6.19-rc7 | 6.19-rc7.x |
| linux / linux_kernel | 6.19-rc8 | 6.19-rc8.x |
A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.
CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.
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Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.
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