Linux Kernel
CVE-2024-36912
CRITICAL
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessMalicious hypervisor hosts CoCo guest
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DeliveryGuest sets up/tears down VMBus GPADL
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ExploitHost forces set_memory_encrypted() to fail
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ExecutionStill-shared page returned to allocator
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ImpactHost reads/tampers reused decrypted memory
Vulnerability Assessment
| Weakness |
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Hardware debug access restrictions
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| Exploitation Conditions | Exploitation requires (1) the Linux guest running the Hyper-V VMBus driver, (2) the guest booted as a Confidential Computing VM with memory encryption (AMD SEV-SNP or Intel TDX) so that set_memory_encrypted()/set_memory_decrypted() are active, and (3) an untrusted/malicious hypervisor host able to force those conversion calls to fail during vmbus_establish_gpadl()/vmbus_teardown_gpadl(). It is strictly limited to this CoCo deployment mode: it is NOT exploitable from the network, NOT from an ordinary unprivileged guest process, and does not apply to conventional (non-encrypted) VMs or bare-metal - the required attacker position is the hypervisor itself, which is the specific adversary CoCo is designed to defend against. |
| Impact | The NVD-assigned CVSS 3.1 score of 9.6 (AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) substantially overstates real-world risk and appears to be an automated Linux-kernel CNA default rather than a considered adjacent-network assessment - the described condition is not reachable over a network and requires a malicious hypervisor, which is only meaningful in the CoCo threat model. Supporting signals agree it is low priority: EPSS is 0.92% (56th percentile), the CVE is NOT in CISA KEV, and no POC is referenced. There is a clear conflict between the CVSS vector (AV:A, PR:N, UI:N implying easy adjacent unauthenticated attack) and the description (requires an untrusted host to fail a memory-conversion operation inside a confidential VM) - verify with the maintainers/threat model before treating the 9.6 as actionable. This is best characterized as a hardening fix that prevents shared pages from leaking into the allocator, not a widely weaponizable vulnerability. |
| Exploit ScenarioDerived | An operator of a malicious or compromised Hyper-V host running a victim Confidential Computing Linux guest repeatedly forces the guest's page-encryption conversion calls to fail during VMBus GPADL teardown. On an unpatched kernel the guest returns a page that is still host-shared (decrypted) to its allocator, where it is later reused for sensitive guest data that the host can then read or tamper with. No public exploit code is referenced, and the attack presupposes host-level control, so it is confined to the confidential-computing threat model. |
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Alert meAnalysisAIv1 – Aug 04, 2026
Memory-safety hardening gap in the Linux kernel's Hyper-V VMBus GPADL handling (Drivers: hv: vmbus) lets an untrusted hypervisor host force set_memory_encrypted()/set_memory_decrypted() to fail inside Confidential Computing (CoCo) guests, so decrypted (shared) pages can be returned to the page allocator on error. The fix adds a decrypted-status field to struct vmbus_gpadl so callers of vmbus_establish_gpadl()/vmbus_teardown_gpadl() can decide to free or deliberately leak affected pages. This is a defense-in-depth fix for the CoCo threat model rather than a conventional remotely exploitable flaw; no public exploit identified at time of analysis and EPSS is low (0.92%, 56th percentile).
RemediationAI
Patch available per vendor advisory: update to a Linux kernel build that includes the vmbus_gpadl decrypted-tracking fix, applied via the kernel.org stable commits 1999644d, 211f514e, 8e62341f, and bfae56be (https://git.kernel.org/stable/c/1999644d95194d4a58d3e80ad04ce19220a01a81 and the three sibling commits) - consume the fix through your distribution's patched stable/LTS kernel rather than building from a specific 6.9 release candidate. Because this only matters inside Confidential Computing guests, the practical compensating control where immediate patching is not possible is to run affected Hyper-V Linux guests without confidential-computing (SEV-SNP/TDX) memory encryption enabled, or on a trusted hypervisor, which removes the untrusted-host precondition entirely; the trade-off is loss of the CoCo confidentiality guarantee, so this is only acceptable in environments where the host is already trusted. No exact tagged release version is stated in the input, so cite the stable commit hashes rather than an invented version number.
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Technical ContextAI · show details
The affected component is the Hyper-V VMBus transport layer (drivers/hv/), which sets up guest-physical-address descriptor lists (GPADLs) to share ring buffers between a Linux guest and the Hyper-V host. In Confidential Computing VMs (AMD SEV-SNP / Intel TDX), guest memory is encrypted by hardware and pages are explicitly toggled shared/private via set_memory_decrypted()/set_memory_encrypted(). Because the host is outside the guest trust boundary, it can induce these calls to fail, leaving a page in the shared (decrypted) state while the guest believes it was re-encrypted. Prior to this change the kernel did not track that state, so an error path could hand a still-shared page back to the allocator for arbitrary reuse. This maps to CWE-1258 (exposure of sensitive information / improper handling of memory state), and the root-cause class is unhandled error returns leaving memory in an inconsistent encryption state.
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Severity by source
AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Attacker must be the untrusted hypervisor and reliably force a memory-conversion failure (AV:L, AC:H, PR:H); impact is mainly disclosure of leaked shared pages (C:H) with limited integrity and no availability effect.
Primary rating from Vendor (416baaa9-dc9f-4396-8d5f-8c081fb06d67).
CVSS VectorVendor: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Lifecycle Timeline
4DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
Drivers: hv: vmbus: Track decrypted status in vmbus_gpadl
In CoCo VMs it is possible for the untrusted host to cause set_memory_encrypted() or set_memory_decrypted() to fail such that an error is returned and the resulting memory is shared. Callers need to take care to handle these errors to avoid returning decrypted (shared) memory to the page allocator, which could lead to functional or security issues.
In order to make sure callers of vmbus_establish_gpadl() and vmbus_teardown_gpadl() don't return decrypted/shared pages to allocators, add a field in struct vmbus_gpadl to keep track of the decryption status of the buffers. This will allow the callers to know if they should free or leak the pages.
Executive ViewAI
A critical memory-safety vulnerability in the Linux kernel's Hyper-V driver (CVE-2024-36912) allows untrusted hypervisor hosts to cause memory decryption failures in confidential computing guests, potentially returning encrypted pages to the general allocator and compromising workload isolation. This affects only organizations running confidential computing on Hyper-V; a patch is available and no public exploit identified at time of analysis.
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Threat Intelligence Overview
NVD
CVE.org
EPSS
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.
GitHub PoC
Exploit-DB