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CVE-2026-74404
crypto: ccp - Fix snp_filter_reserved_mem_regions() off-by-one
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem drivers/crypto. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-74404 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 | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Sashiko notes: > regarding the bounds check in snp_filter_reserved_mem_regions() > called via walk_iomem_res_desc(): does the check > if ((range_list->num_elements * 16 + 8) > PAGE_SIZE) > allow an off-by-one heap buffer overflow? > > If range_list->num_elements is 255, 255 * 16 + 8 = 4088, which is <= 4096. > Writing range->base (8 bytes) fills 4088-4095, but writing range->page_count > (4 bytes) would write to 4096-4099, overflowing the kzalloc-allocated > PAGE_SIZE buffer. Fix this by accounting for the entry about to be written to, in addition to the entries that are already allocated.
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/crypto/ccp/sev-dev.c
- What this is
- AMD CRYPTOGRAPHIC COPROCESSOR (CCP) DRIVER - SEV SUPPORTMAINTAINERS section matched on drivers/crypto/ccp/sev* · linux-crypto@vger.kernel.org · Supported
- Kernel module
- ccp
Check it on the machine
grep -wE 'CONFIG_CRYPTO|CONFIG_CRYPTO_DEV_CCP|CONFIG_CRYPTO_DEV_CCP_DD|CONFIG_CRYPTO_DEV_SP_PSP' /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 ccpPrints 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 amd64/cloud-amd64, 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 amd64/cloud-amd64, 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_CRYPTO, CONFIG_CRYPTO_DEV_CCP, CONFIG_CRYPTO_DEV_CCP_DD, CONFIG_CRYPTO_DEV_SP_PSP
- 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
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.19%, higher than 8.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/crypto
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.9 | 6.12.97 | 830c1f3e7198 |
| 6.9 | 6.18.40 | c5c79d92da0f |
| 6.9 | 7.1.5 | af7341616b74 |
| 6.9 | 7.2 | 1b864b6cb213 |
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 overflow is reached only via local host paths—KVM VM ioctl KVM_SEV_INIT2 (sev_guest_init2→sev_platform_init→__sev_snp_init_locked) or kernel boot-time SEV-SNP platform init—not through any network, Bluetooth, or physical bus handler.
- AC:LAttack complexity, low
- Once on an AMD SEV-SNP host with SNP firmware ≥1.52, a caller can deterministically trigger SNP_INIT_EX initialization via KVM_SEV_INIT2; no race or attacker-uncontrollable timing is required, only a firmware memory map with ≥256 matching reserved/ACPI/PMEM iomem regions.
- PR:LPrivileges required, low
- Exploitation requires local hypervisor access to create an SNP-capable KVM VM and issue KVM_SEV_INIT2 (typical /dev/kvm or kvm-group hypervisor operator), not unauthenticated remote access; comparable KVM ioctl CVEs in this repo score this as low privilege rather than init-namespace root only.
- UI:NUser interaction, none
- No victim interaction is needed beyond the attacker (or boot sequence) invoking SNP platform initialization; the bug fires automatically while enumerating the system iomem map during SNP_INIT_EX setup.
- S:UScope, unchanged
- The corruption occurs in host kernel heap memory during hypervisor SEV-SNP platform initialization by a host-side caller; it is not a guest-to-host VM escape, IOMMU/DMA bypass, or cross-authority sandbox breakout.
- C:HConfidentiality impact, high
- The off-by-one permits a 4-byte out-of-bounds write of page_count past a PAGE_SIZE kzalloc buffer, corrupting adjacent kmalloc slab memory in ways that can be leveraged for kernel information disclosure.
- I:HIntegrity impact, high
- A controlled heap buffer overflow (even 4 bytes) can corrupt adjacent kernel objects and be developed into arbitrary kernel memory writes or control-flow hijacking, satisfying high integrity impact per kernel OOB-write guidance.
- A:HAvailability impact, high
- Heap metadata/object corruption during SNP_INIT_EX can cause kernel oops/panic or leave the host in a failed state, especially on confidential-computing servers where SNP initialization is on the critical boot/VM-launch path.