CVE-2026-90040 Vulnerability Analysis & Exploit Details

CVE-2026-90040
Vulnerability Scoring

Analysis In Progress

Attack Complexity Details

Attack Complexity:
Attack Complexity Analysis In Progress
Attack Vector:
Attack Vector Under Analysis
Privileges Required: None
No authentication is required for exploitation.
Scope:
Impact is confined to the initially vulnerable component.
User Interaction: None
No user interaction is necessary for exploitation.

CVE-2026-90040 Details

Status: Received on 16 Sep 2026, 11:17 UTC

Published on: 16 Sep 2026, 11:17 UTC

CVSS Release:

CVE-2026-90040 Vulnerability Summary

CVE-2026-90040: In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Forcefully invalidate SNP VMSA if its backing gmem page is zapped Wire up a gmem_invalidate_range() call for SNP VMs, and use it to force vCPUs to reload/recheck their guest-provided VMSA if the backing gmem page is being invalidated, e.g. is being PUNCH_HOLE'd. Use the same core logic to handle invalidations as VMX does for the APIC-access page, as the two concepts are nearly identical: shove the physical address of a page into the vCPU's control structure: 1. Snapshot the invalidation sequence counter 2. Grab the pfn (from guest_memfd in this case) 3. Acquire mmu_lock for read 4. Re-request reload if retry is needed, otherwise commit the change. Note, the re-request action in #4 is necessary as KVM's retry logic is fuzzy, i.e. can get false positives. If the guest_memfd page has been dropped, at some point a subsequent reload will fail to get a PFN from guest_memfd, and KVM will fail KVM_RUN. If the retry was due to a false positive, KVM will retry until there are no relevant MMU notifier events (and will retry in the "outer" loop, i.e. will drop locks and resched as needed). Note #2! Take care to invalidate the VMSA when a relevant memslot is DELETED or MOVED, as invalidations in response to PUNCH_HOLE are predicated on memslot bindings (KVM doesn't know what GFN range(s) to invalidate without a binding). And more importantly, the VMSA mapping requires a memslot, i.e. must be invalidated if its memslots disappears, regardless of the state of the underlying guest_memfd inode. Failure to invalidate the vCPU's control.vmsa_pa (which is checked by pre_sev_run()) can prevent KVM from properly freeing the page as firmware will reject the RMPUPDATE to reclaim the page with FAIL_INUSE if the vCPU is actively running, i.e. if VMSA page is in-use. That in turn leads to an RMP #PF on the next use, as the page will still be assigned to the SNP VM. SEV-SNP: RMPUPDATE failed for PFN 78d198, pg_level: 1, ret: 3 SEV-SNP: PFN 0x78d198, RMP entry: [0xfff0000000144001 - 0x000000000000000f] CPU: 3 UID: 0 PID: 31345 Comm: sev_snp_vmsa_pu Tainted: G U O Tainted: [U]=USER, [O]=OOT_MODULE Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.86.0-102 01/25/2026 Call Trace: <TASK> dump_stack_lvl+0x54/0x70 rmpupdate+0x12c/0x140 rmp_make_shared+0x3b/0x60 sev_gmem_invalidate+0xe0/0x170 [kvm_amd] delete_from_page_cache_batch+0x1d8/0x220 truncate_inode_pages_range+0x120/0x3d0 kvm_gmem_fallocate+0x19a/0x270 [kvm] vfs_fallocate+0x1bc/0x1f0 __x64_sys_fallocate+0x48/0x70 do_syscall_64+0x10a/0x480 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x496c7e </TASK> ------------[ cut here ]------------ SEV: Failed to update RMP entry for PFN 0x78d198 error -14 WARNING: arch/x86/kvm/svm/sev.c:5160 at sev_gmem_invalidate+0x126/0x170 [kvm_amd], CPU#3: sev_snp_vmsa_pu/31345 CPU: 3 UID: 0 PID: 31345 Comm: sev_snp_vmsa_pu Tainted: G U O Tainted: [U]=USER, [O]=OOT_MODULE Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.86.0-102 01/25/2026 RIP: 0010:sev_gmem_invalidate+0x12b/0x170 [kvm_amd] Call Trace: <TASK> delete_from_page_cache_batch+0x1d8/0x220 truncate_inode_pages_range+0x120/0x3d0 kvm_gmem_fallocate+0x19a/0x270 [kvm] vfs_fallocate+0x1bc/0x1f0 __x64_sys_fallocate+0x48/0x70 do_syscall_64+0x10a/0x480 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x496c7e </TASK> irq event stamp: 20689 hardirqs last enabled at (20699): [<ffffffff8e76092c>] __console_unlock+0x5c/0x60 hardirqs last disabled at (20708): [<ffffffff8e760911>] __console_unlock+0x41/0x60 softirqs last enabled at (20722): [<ffffffff8e6cd74e>] __irq_exit_rcu+0x7e/0x140 softirqs last disabled at (20717): [<ffffffff8e6cd74e>] __irq_exit_rcu+0x7e/0x140 ---[ end trace 0000000000000000 ]--- BUG: unable to handle page fault for address: ffff99 ---truncated---

Assessing the Risk of CVE-2026-90040

Access Complexity Graph

The exploitability of CVE-2026-90040 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2026-90040

No exploitability data is available for CVE-2026-90040.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2026-90040, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2026-90040, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

Confidentiality: None
CVE-2026-90040 does not compromise confidentiality.
Integrity: None
CVE-2026-90040 does not impact data integrity.
Availability: None
CVE-2026-90040 does not affect system availability.

CVE-2026-90040 References

External References

CWE Common Weakness Enumeration

Unknown

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