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CVE-2026-74607
KVM: SVM: Serialize accesses to the owner and mirror list with separate lock
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem arch/x86. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74607 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6466-1 · 2026-08-25 · text | 6.12.105-1 | Update the kernel and reboot. DSA-6466-1 shipped the fix on 2026-08-25, in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Interaction between KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM and KVM_CAP_VM_COPY_ENC_CONTEXT_FROM can cause two separate issues: - in sev_migrate_from(), when the destination KVM is a mirror, the mirror entry is moved from the source's list to the owner's mirror_vms list, without holding the owner's lock unlike other writers of the owner's mirror list (sev_vm_copy_enc_context_from(), sev_vm_destroy()). A concurrent COPY or destroy can race with sev_migrate_from() and corrupt the list. - In sev_vm_destroy(), the *owner* is still active and could receive concurrently a KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM that causes sev->enc_context_owner to change. In this case the incorrect VM receives kvm_put_kvm(). The second issue needs particular care because the owner could disappear altogether (even though the race window is impossibly small) between reading it and locking it. There is thus no way to perform the checks under the owner lock without putting struct kvm under SLAB_TYPESAFE_BY_RCU (which would allow kvm_get_kvm_safe() under RCU critical section). It is much simpler to just use a global lock, since the critical sections are so small and the new lock is always a leaf lock.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
arch/x86/kvm/svm/sev.c
arch/x86/kvm/svm/svm.h
- What this is
- KERNEL VIRTUAL MACHINE FOR X86 (KVM/x86)MAINTAINERS section matched on arch/x86/kvm/*/ · kvm@vger.kernel.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid, bookworm · linux-6.12?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-08-22 (2 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- arch/x86
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.18 | 6.1.184 | 7943ec3a6d0e |
| 5.18 | 6.6.153 | 28afde1edbd8 |
| 5.18 | 6.12.105 | 328ab4fabe05 |
| 5.18 | 6.18.45 | 47976eaaf0a4 |
| 5.18 | 7.1.9 | d728baba0f20 |
| 5.18 | 7.2 | 1d78d33275ef |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DSA-6466-1 | 2026-08-25 | trixie 6.12.105-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- Reached only via local KVM_ENABLE_CAP ioctl on VM fds (KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM/KVM_CAP_VM_COPY_ENC_CONTEXT_FROM) after opening /dev/kvm; not network, adjacent-wireless, or physical-device reachable.
- AC:LAttack complexity, low
- Attacker with multiple VM fds can concurrently issue MOVE, COPY, and close operations from threads they control to deterministically race sev_migrate_from(), sev_vm_copy_enc_context_from(), and sev_vm_destroy().
- PR:LPrivileges required, low
- Requires /dev/kvm and SEV setup (typically kvm-group or QEMU/container KVM passthrough), not init-namespace root; CAP_SYS_ADMIN-equivalent access is not obtainable via unprivileged user namespaces alone but kvm tenants hold sufficient access.
- UI:NUser interaction, none
- No victim interaction; the attacker VMM process issues the ioctl sequence and concurrent close/migrate operations directly.
- S:CScope, changed
- Races corrupt SEV mirror/owner linked lists and can misdirect kvm_put_kvm() on the wrong struct kvm, breaking AMD SEV encrypted-memory isolation boundaries and enabling host impact beyond the caller VM scope.
- C:HConfidentiality impact, high
- Unsynchronized mirror_vms/enc_context_owner updates cause kernel linked-list corruption and kvm refcount UAF, which can disclose kernel memory and confidential SEV guest ciphertext via broken owner/mirror bookkeeping.
- I:HIntegrity impact, high
- List corruption and mistaken kvm_put_kvm() on the wrong KVM object provide exploitable heap corruption and control over SEV encryption context lifetime, enabling arbitrary host memory modification.
- A:HAvailability impact, high
- Corrupted mirror lists, use-after-free on struct kvm, or premature destruction of an active SEV owner/mirror reliably triggers kernel oops/panic and denial of host service.