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CVE-2026-64104
virt: sev-guest: Explicitly leak pages in unknown state
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/virt. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64104 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When set_memory_{encrypted,decrypted}() fail, the user cannot know at which point the function failed, meaning that the pages are left in an unknown state from the point of view of the caller. Since the pages may be left in an unencrypted state, they are not suitable for general use, and cannot be returned safely to the buddy allocator. Avoid the issue by never freeing the pages, and then do the proper accounting by calling snp_leak_pages().
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.
drivers/virt/coco/sev-guest/sev-guest.c
- What this is
- THE RESTMAINTAINERS section matched on */ · linux-kernel@vger.kernel.org · Buried alive in reporters
- Kernel module
- sev_guest
Check it on the machine
grep -wE 'CONFIG_SEV_GUEST|CONFIG_VIRT_DRIVERS' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w sev_guestPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormMnot built on amd64/cloud-amd64, arm64/arm64, arm64/cloud-arm64, arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixieMnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt/arm64, armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidMnot built on arm64/arm64, arm64/arm64-16k, arm64/cloud-arm64, arm64/rt-arm64, armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_SEV_GUEST, CONFIG_VIRT_DRIVERS
- Reads as
- all on means the file is compiled; any one off means it is not.
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 kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-19 (3 months ago)source
- CVSS
- 8.7 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Lsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.8% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/virt
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.14 | 6.18.34 | bee400ad4f42 |
| 6.14 | 7.0.11 | 3d0cd0065dee |
| 6.14 | 7.1 | fd948c3f96b1 |
| 6.13.8 | 0 | 0 |
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
- The bug is in `get_ext_report()` and is reached only via `SNP_GET_EXT_REPORT` ioctl on `/dev/sev-guest` (or the kernel-internal configfs-TSM path), which requires local access inside an AMD SEV-SNP confidential guest VM.
- AC:LAttack complexity, low
- A local caller can repeatedly issue `SNP_GET_EXT_REPORT` with a non-zero, page-aligned `certs_len` to drive allocation and `set_memory_decrypted()`/`set_memory_encrypted()`; on failure after `snp_set_memory_shared()` has already run, the pre-fix path incorrectly returned those pages to the buddy allocator.
- PR:LPrivileges required, low
- Exploitation requires opening `/dev/sev-guest` and issuing the ioctl; in typical confidential-VM deployments attestation is performed by unprivileged workloads, and the ioctl path does not require real root in the init namespace.
- UI:NUser interaction, none
- Triggering the vulnerable cleanup requires only programmatic ioctl calls to obtain an extended attestation report; no victim user action such as mounting a filesystem or opening a file is needed.
- S:CScope, changed
- Returning pages that may remain in shared/unencrypted RMP state to the buddy allocator breaks the SEV-SNP guest-to-hypervisor memory confidentiality boundary, allowing a malicious or compromised hypervisor to read (and tamper with) guest kernel memory later allocated on those pages.
- C:HConfidentiality impact, high
- Pages can be left hypervisor-visible while re-entering the general kernel page pool, enabling disclosure of arbitrary subsequent guest kernel memory contents (keys, crypto material, process data) to the untrusted host.
- I:HIntegrity impact, high
- Shared RMP pages reused by the kernel can be modified by the hypervisor before the guest reads them, providing a write primitive against guest kernel memory that can undermine integrity of kernel data structures and potentially enable further compromise.
- A:LAvailability impact, low
- The flaw does not directly panic the kernel, but repeated triggering of the error path can stress page accounting and, in worst cases, contribute to allocator instability; availability impact is limited rather than a reliable crash.