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Fencer Vulns
high 8.8

CVE-2026-53360 json

KVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use

published 2026-07-04 4 mo ago modified 2026-10-19 20 d ago also EUVD-2026-41667

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

In the Linux kernel, the following vulnerability has been resolved:

KVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use

As per the GHCB spec, when using GHCB v2+ require the software scratch area to reside in the GHCB's shared buffer. Note, things like Page State Change (PSC) requests _rely_ on this behavior, as the guest can't provide a length when making the request, i.e. the size of the guest payload is bounded by the size of the shared buffer.

Failure to force usage of the GHCB, and a slew of other flaws, lets a malicious SNP guest corrupt host kernel heap memory, and leak host heap layout information.

setup_vmgexit_scratch() allocates a buffer via kvzalloc(exit_info_2), where exit_info_2 is guest-controlled. With exit_info_2=24, this yields a 24-byte allocation in kmalloc-cg-32 (32-byte slab objects). The buffer holds an 8-byte psc_hdr followed by 8-byte psc_entry structs, so only entries[0] and entries[1] are in-bounds.

snp_begin_psc() validates end_entry against VMGEXIT_PSC_MAX_COUNT (253) but NOT against the actual buffer size:

idx_end = hdr->end_entry;

if (idx_end >= VMGEXIT_PSC_MAX_COUNT) { // checks 253, not buffer snp_complete_psc(svm, ...); return 1; }

for (idx = idx_start; idx <= idx_end; idx++) { entry_start = entries[idx]; // OOB when idx >= 2

The guest sets end_entry=10+, causing the host to iterate entries[2+] which are OOB into adjacent slab objects. For each OOB entry:

- The host reads 8 bytes (OOB READ / info leak oracle) - If the data passes PSC validation, __snp_complete_one_psc() writes cur_page = 1 or 512 into the entry (OOB WRITE, sev.c:3806) - If validation fails, the error response reveals whether adjacent memory is zero vs non-zero (information disclosure to guest)

The guest controls allocation size (exit_info_2), entry range (cur_entry/end_entry), and can fire unlimited VMGEXITs to repeatedly hit different slab positions.

By exploiting the variety of bugs, a malicious SEV-SNP guest can: - OOB read adjacent kmalloc-cg-32 objects (heap layout disclosure) - OOB write cur_page bits into adjacent objects (heap corruption) - Trigger use-after-free conditions across VMGEXITs

E.g. with KASAN enabled, a single insmod of the PoC guest module produces 73 KASAN reports:

BUG: KASAN: slab-out-of-bounds in snp_begin_psc+0x126/0x890 Read of size 8 at addr ffff888219ffb5e0 by task qemu-system-x86/2199

BUG: KASAN: slab-out-of-bounds in snp_begin_psc+0x468/0x890 Write of size 8 at addr ffff888351566648 by task qemu-system-x86/2199

The buggy address belongs to the object at ffff888XXXXXXXXX which belongs to the cache kmalloc-cg-32 of size 32 The buggy address is located N bytes to the right of allocated 32-byte region [ffff888XXXXXXXXX, ffff888XXXXXXXXX)

Breakdown: 62 slab-out-of-bounds (reads + writes past allocation) 7 slab-use-after-free 4 use-after-free

All credit to Stan for the wonderful description and reproducer!

[sean: write changelog]

Patch / fix

  • Linux Linux 6.12.93, 6.18.35, 7.0.12, 7.1
  • linux Debian 13 6.12.94-1
  • linux Debian 14 7.0.12-1

debian advisories DEBIAN-CVE-2026-53360

  • linux Ubuntu 26.04 LTS 7.0.0-28.28
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1009.9
  • linux-gcp Ubuntu 26.04 LTS 7.0.0-1008.8
  • linux-gke Ubuntu 26.04 LTS 7.0.0-1003.4
  • linux-ibm Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-azure Ubuntu 26.04 LTS 7.0.0-1010.10
  • linux-raspi Ubuntu 26.04 LTS 7.0.0-1015.15
  • linux-riscv Ubuntu 26.04 LTS 7.0.0-28.28.1

ubuntu advisories UBUNTU-CVE-2026-53360

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel RHEL 10.2 6.12.0-211.64.1.el10_2
  • rv RHEL 10.2 6.12.0-211.64.1.el10_2
  • perf RHEL 10.2 6.12.0-211.64.1.el10_2
  • rtla RHEL 10.2 6.12.0-211.64.1.el10_2
  • libperf RHEL 10.2 6.12.0-211.64.1.el10_2
  • kernel-rt RHEL 10.2 6.12.0-211.64.1.el10_2
  • kernel-64k RHEL 10.2 6.12.0-211.64.1.el10_2
  • kernel-core RHEL 10.2 6.12.0-211.64.1.el10_2

red hat advisories RHSA-2026:77690RHSA-2026:77689

  • kernel-livepatch-SLE16_Update_5 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 11-160000.1.1
  • kernel-livepatch-SLE16_Update_4 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 12-160000.1.1
  • kernel-livepatch-SLE16_Update_3 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 13-160000.1.1
  • kernel-livepatch-SLE16_Update_2 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 14-160000.1.1
  • kernel-livepatch-SLE16_Update_10 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 7-160000.1.1
  • kernel-livepatch-SLE16_Update_9 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 7-160000.1.1
  • kernel-livepatch-SLE16_Update_1 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 16-160000.1.1
  • kernel-livepatch-SLE16_Update_0 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 18-160000.4.3

suse advisories SUSE-SU-2026:23944-1SUSE-SU-2026:23967-1SUSE-SU-2026:23942-1SUSE-SU-2026:23966-1SUSE-SU-2026:23941-1SUSE-SU-2026:23965-1

  • kernel-rt openSUSE Leap 16.0 6.12.0-160000.37.1
  • dtb-aarch64 openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-64kb openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-syms openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-azure openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-obs-qa openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-source openSUSE Leap 16.0 6.12.0-160000.37.1
  • kernel-default openSUSE Leap 16.0 6.12.0-160000.37.1

opensuse advisories openSUSE-SU-2026:21555-1

  • kernel AlmaLinux 9 5.14.0-687.56.1.el9_8
  • rv AlmaLinux 9 5.14.0-687.56.1.el9_8
  • perf AlmaLinux 9 5.14.0-687.56.1.el9_8
  • rtla AlmaLinux 9 5.14.0-687.56.1.el9_8
  • libperf AlmaLinux 9 5.14.0-687.56.1.el9_8
  • kernel-rt AlmaLinux 9 5.14.0-687.56.1.el9_8
  • kernel-64k AlmaLinux 9 5.14.0-687.56.1.el9_8
  • kernel-core AlmaLinux 9 5.14.0-687.56.1.el9_8

almalinux advisories ALSA-2026:77689ALSA-2026:77690

  • kernel Rocky Linux 10 6.12.0-211.64.1.el10_2
  • kernel Rocky Linux 9 5.14.0-687.56.1.el9_8

rocky linux advisories RLSA-2026:77690RLSA-2026:77689

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-53360 updated cvss 8.8

kernel: KVM: SEV: Require in-GHCB scratch area if GHCB v2+ is in use

  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.64.1.el10_2
    fixed: vendor fix RHSA-2026:77690
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.56.1.el9_8, perf 5.14.0-687.56.1.el9_8, rtla 5.14.0-687.56.1.el9_8, python3-perf 5.14.0-687.56.1.el9_8, kernel-devel-matched 5.14.0-687.56.1.el9_8, kernel-64k-devel-matched 5.14.0-687.56.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:77689
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.64.1.el10_2, perf 6.12.0-211.64.1.el10_2, rtla 6.12.0-211.64.1.el10_2, python3-perf 6.12.0-211.64.1.el10_2, kernel-devel-matched 6.12.0-211.64.1.el10_2, kernel-64k-devel-matched 6.12.0-211.64.1.el10_2, +7 more
    fixed: vendor fix RHSA-2026:77690
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.56.1.el9_8, kernel-64k 5.14.0-687.56.1.el9_8, kernel-core 5.14.0-687.56.1.el9_8, kernel-tools 5.14.0-687.56.1.el9_8, kernel-modules 5.14.0-687.56.1.el9_8, kernel-64k-core 5.14.0-687.56.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:77689
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.64.1.el10_2, kernel-64k 6.12.0-211.64.1.el10_2, kernel-core 6.12.0-211.64.1.el10_2, kernel-tools 6.12.0-211.64.1.el10_2, kernel-modules 6.12.0-211.64.1.el10_2, kernel-64k-core 6.12.0-211.64.1.el10_2, +28 more
    fixed: vendor fix RHSA-2026:77690
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.56.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.56.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.56.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.56.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.56.1.el9_8
    fixed: vendor fix RHSA-2026:77689
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.64.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-211.64.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.64.1.el10_2, kernel-debuginfo-common-aarch64 6.12.0-211.64.1.el10_2, kernel-debuginfo-common-ppc64le 6.12.0-211.64.1.el10_2 Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.64.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.64.1.el10_2
    fixed: vendor fix RHSA-2026:77690
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.56.1.el9_8, kernel-rt-64k 5.14.0-687.56.1.el9_8, kernel-rt-core 5.14.0-687.56.1.el9_8, kernel-rt-modules 5.14.0-687.56.1.el9_8, kernel-rt-64k-core 5.14.0-687.56.1.el9_8, kernel-rt-debug-core 5.14.0-687.56.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:77689
show 4 more
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.64.1.el10_2, kernel-rt-64k 6.12.0-211.64.1.el10_2, kernel-rt-core 6.12.0-211.64.1.el10_2, kernel-rt-modules 6.12.0-211.64.1.el10_2, kernel-rt-64k-core 6.12.0-211.64.1.el10_2, kernel-rt-debug-core 6.12.0-211.64.1.el10_2, +14 more
    fixed: vendor fix RHSA-2026:77690
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.56.1.el9_8, kernel-rt-core 5.14.0-687.56.1.el9_8, kernel-rt-modules 5.14.0-687.56.1.el9_8, kernel-rt-debug-core 5.14.0-687.56.1.el9_8, kernel-rt-modules-core 5.14.0-687.56.1.el9_8, kernel-rt-debug-modules 5.14.0-687.56.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:77689
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.64.1.el10_2, kernel-rt-core 6.12.0-211.64.1.el10_2, kernel-rt-modules 6.12.0-211.64.1.el10_2, kernel-rt-debug-core 6.12.0-211.64.1.el10_2, kernel-rt-modules-core 6.12.0-211.64.1.el10_2, kernel-rt-debug-modules 6.12.0-211.64.1.el10_2, +4 more
    fixed: vendor fix RHSA-2026:77690
  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 kernel-rt, kernel-rt-kvm, kernel-rt-core, kernel-rt-modules, kernel-rt-debug-kvm, kernel-rt-debug-core, +12 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.