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high 7.8

CVE-2026-63794 json

KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path

published 3mo ago modified 5d ago also EUVD-2026-45460

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

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

KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path

In sev_dbg_crypt(), the per-iteration transfer length is bounded by the source page offset (PAGE_SIZE - s_off) but not by the destination page offset (PAGE_SIZE - d_off). When d_off > s_off, the encrypt path (__sev_dbg_encrypt_user) performs a read-modify-write using a single-page intermediate buffer (dst_tpage):

1. __sev_dbg_decrypt() expands the size to round_up(len + (d_off & 15), 16) before issuing the PSP command. If len + (d_off & 15) > PAGE_SIZE, the PSP writes beyond the end of the 4096-byte dst_tpage allocation.

2. The subsequent memcpy()/copy_from_user() into page_address(dst_tpage) + (d_off & 15) of 'len' bytes overflows by up to 15 bytes under the same condition.

Trigger example: s_off = 0, d_off = 1, debug.len = PAGE_SIZE - the PSP is instructed to write round_up(4097, 16) = 4112 bytes to a 4096-byte buffer.

Fix by also bounding len by (PAGE_SIZE - d_off), the same check that sev_send_update_data() already performs for its single-page guest region.

================================================================== BUG: KASAN: slab-use-after-free in sev_dbg_crypt+0x993/0xd10 [kvm_amd] Write of size 4095 at addr ff110062293bb009 by task sev_dbg_test/228214

CPU: 96 UID: 0 PID: 228214 Comm: sev_dbg_test Tainted: G U W 7.0.0-smp--5ce9b0c48211-dbg #156 PREEMPTLAZY Tainted: [U]=USER, [W]=WARN Hardware name: Google Astoria/astoria, BIOS 0.20250817.1-0 08/25/2025 Call Trace: <TASK> dump_stack_lvl+0x54/0x70 print_report+0xbc/0x260 kasan_report+0xa2/0xd0 kasan_check_range+0x25f/0x2c0 __asan_memcpy+0x40/0x70 sev_dbg_crypt+0x993/0xd10 [kvm_amd] sev_mem_enc_ioctl+0x33c/0x450 [kvm_amd] kvm_vm_ioctl+0x65d/0x6d0 [kvm] __se_sys_ioctl+0xb2/0x100 do_syscall_64+0xe8/0x870 entry_SYSCALL_64_after_hwframe+0x4b/0x53 </TASK>

The buggy address belongs to the physical page: page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7fe72b6a0 pfn:0x62293bb memcg:ff11000112827d82 flags: 0x1400000000000000(node=1|zone=1) raw: 1400000000000000 0000000000000000 dead000000000122 0000000000000000 raw: 00000007fe72b6a0 0000000000000000 00000001ffffffff ff11000112827d82 page dumped because: kasan: bad access detected

Memory state around the buggy address: ff110062293bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ff110062293bbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >ff110062293bc000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ^ ff110062293bc080: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ff110062293bc100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ================================================================== Disabling lock debugging due to kernel taint

[sean: add sample KASAN splat, Fixes, and stable@]

Patch / fix

  • Linux Linux 5.10.260, 5.15.211, 6.1.177, 6.6.144, 6.12.95, 6.18.38, 7.1.3, 7.2
  • linux Debian 12 6.1.177-1
  • linux Debian 13 6.12.95-1
  • linux Debian 14 7.1.3-1

debian advisories DEBIAN-CVE-2026-63794

  • linux Ubuntu 22.04 LTS 5.15.0-198.208
  • linux Ubuntu 24.04 LTS 6.8.0-147.147
  • linux Ubuntu 26.04 LTS 7.0.0-31.31
  • linux-aws Ubuntu 22.04 LTS 5.15.0-1117.124
  • linux-aws Ubuntu 24.04 LTS 6.8.0-1067.70
  • linux-aws Ubuntu 26.04 LTS 7.0.0-1012.12
  • linux-gcp Ubuntu 22.04 LTS 5.15.0-1118.128
  • linux-gcp Ubuntu 24.04 LTS 6.8.0-1071.79

ubuntu advisories UBUNTU-CVE-2026-63794

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 8 4.18.0-553.171.1.el8_10
  • perf RHEL 8 4.18.0-553.171.1.el8_10
  • bpftool RHEL 8 4.18.0-553.171.1.el8_10
  • kernel-core RHEL 8 4.18.0-553.171.1.el8_10
  • kernel-tools RHEL 8 4.18.0-553.171.1.el8_10
  • python3-perf RHEL 8 4.18.0-553.171.1.el8_10
  • kernel-modules RHEL 8 4.18.0-553.171.1.el8_10
  • kernel-zfcpdump RHEL 8 4.18.0-553.171.1.el8_10

red hat advisories RHSA-2026:75747RHSA-2026:75746RHSA-2026:74438

  • kernel-livepatch-SLE16_Update_10 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 9-160000.1.1
  • kernel-livepatch-SLE16_Update_1 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 18-160000.1.1
  • kernel-livepatch-SLE16_Update_5 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 13-160000.1.1
  • kernel-livepatch-SLE16_Update_8 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 10-160000.1.1
  • kernel-livepatch-SLE16_Update_11 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 9-160000.1.1
  • kernel-livepatch-SLE16_Update_0 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 20-160000.4.3
  • kernel-livepatch-SLE16_Update_2 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 16-160000.1.1
  • kernel-livepatch-SLE16_Update_6 SLES 16.0, Linux Micro 6.2, SLES for SAP applications 16.0 12-160000.1.1

suse advisories SUSE-SU-2026:24431-1SUSE-SU-2026:24455-1SUSE-SU-2026:24434-1SUSE-SU-2026:24458-1SUSE-SU-2026:24433-1SUSE-SU-2026:24457-1

  • 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-2026:21555-1openSUSE-SU-2026:11339-1

  • kernel AlmaLinux 10 6.12.0-211.63.1.el10_2
  • rv AlmaLinux 10 6.12.0-211.63.1.el10_2
  • perf AlmaLinux 10 6.12.0-211.63.1.el10_2
  • rtla AlmaLinux 10 6.12.0-211.63.1.el10_2
  • libperf AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-rt AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-64k AlmaLinux 10 6.12.0-211.63.1.el10_2
  • kernel-core AlmaLinux 10 6.12.0-211.63.1.el10_2

almalinux advisories ALSA-2026:76738ALSA-2026:75746ALSA-2026:75747ALSA-2026:74438

  • kernel-rt Rocky Linux 8 4.18.0-553.171.1.rt7.512.el8_10
  • kernel Rocky Linux 8 4.18.0-553.171.1.el8_10
  • kernel Rocky Linux 9 5.14.0-687.54.1.el9_8

rocky linux advisories RLSA-2026:75746RLSA-2026:75747RLSA-2026:74438

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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-2026-63794 updated cvss 7.0

kernel: KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path

  • 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
    affected: no fix available
  • Red Hat Enterprise Linux kernel-modules-internal 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux AppStream (v. 9) rv 5.14.0-687.54.1.el9_8, perf 5.14.0-687.54.1.el9_8, rtla 5.14.0-687.54.1.el9_8, python3-perf 5.14.0-687.54.1.el9_8, kernel-devel-matched 5.14.0-687.54.1.el9_8, kernel-64k-devel-matched 5.14.0-687.54.1.el9_8, +7 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux AppStream (v. 10) rv 6.12.0-211.63.1.el10_2, rv 6.12.0-264.14.1.el10_3, perf 6.12.0-211.63.1.el10_2, perf 6.12.0-264.14.1.el10_3, rtla 6.12.0-211.63.1.el10_2, rtla 6.12.0-264.14.1.el10_3, +20 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.171.1.el8_10, kernel 4.18.0-553.171.1.el8_10, bpftool 4.18.0-553.171.1.el8_10, kernel-core 4.18.0-553.171.1.el8_10, kernel-tools 4.18.0-553.171.1.el8_10, python3-perf 4.18.0-553.171.1.el8_10, +15 more
    fixed: vendor fix RHSA-2026:75747
  • Red Hat Enterprise Linux BaseOS (v. 9) kernel 5.14.0-687.54.1.el9_8, kernel-64k 5.14.0-687.54.1.el9_8, kernel-core 5.14.0-687.54.1.el9_8, kernel-tools 5.14.0-687.54.1.el9_8, kernel-modules 5.14.0-687.54.1.el9_8, kernel-64k-core 5.14.0-687.54.1.el9_8, +27 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux BaseOS (v. 10) kernel 6.12.0-211.63.1.el10_2, kernel 6.12.0-264.14.1.el10_3, kernel-64k 6.12.0-211.63.1.el10_2, kernel-64k 6.12.0-264.14.1.el10_3, kernel-core 6.12.0-211.63.1.el10_2, kernel-core 6.12.0-264.14.1.el10_3, +62 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) libperf 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-s390x 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-x86_64 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-aarch64 5.14.0-687.54.1.el9_8, kernel-debuginfo-common-ppc64le 5.14.0-687.54.1.el9_8
    fixed: vendor fix RHSA-2026:74438
show 10 more
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libperf 6.12.0-211.63.1.el10_2, libperf 6.12.0-264.14.1.el10_3, kernel-debuginfo-common-s390x 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-s390x 6.12.0-264.14.1.el10_3, kernel-debuginfo-common-x86_64 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-264.14.1.el10_3, +4 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.171.1.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.171.1.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.171.1.el8_10
    fixed: vendor fix RHSA-2026:75747
  • Red Hat Enterprise Linux Hidden (v. 10) kernel-modules-internal 6.12.0-211.63.1.el10_2, kernel-debuginfo-common-x86_64 6.12.0-211.63.1.el10_2
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-kvm 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-core 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-modules 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-debug-kvm 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-debug-core 4.18.0-553.171.1.rt7.512.el8_10, +4 more
    fixed: vendor fix RHSA-2026:75746
  • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt 5.14.0-687.54.1.el9_8, kernel-rt-64k 5.14.0-687.54.1.el9_8, kernel-rt-core 5.14.0-687.54.1.el9_8, kernel-rt-modules 5.14.0-687.54.1.el9_8, kernel-rt-64k-core 5.14.0-687.54.1.el9_8, kernel-rt-debug-core 5.14.0-687.54.1.el9_8, +14 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt 6.12.0-211.63.1.el10_2, kernel-rt 6.12.0-264.14.1.el10_3, kernel-rt-64k 6.12.0-211.63.1.el10_2, kernel-rt-64k 6.12.0-264.14.1.el10_3, kernel-rt-core 6.12.0-211.63.1.el10_2, kernel-rt-core 6.12.0-264.14.1.el10_3, +34 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt 5.14.0-687.54.1.el9_8, kernel-rt-core 5.14.0-687.54.1.el9_8, kernel-rt-modules 5.14.0-687.54.1.el9_8, kernel-rt-debug-core 5.14.0-687.54.1.el9_8, kernel-rt-modules-core 5.14.0-687.54.1.el9_8, kernel-rt-debug-modules 5.14.0-687.54.1.el9_8, +4 more
    fixed: vendor fix RHSA-2026:74438
  • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt 6.12.0-211.63.1.el10_2, kernel-rt 6.12.0-264.14.1.el10_3, kernel-rt-core 6.12.0-211.63.1.el10_2, kernel-rt-core 6.12.0-264.14.1.el10_3, kernel-rt-modules 6.12.0-211.63.1.el10_2, kernel-rt-modules 6.12.0-264.14.1.el10_3, +15 more
    fixed: vendor fix RHSA-2026:76738
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-core 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-modules 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-debug-core 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-debug-modules 4.18.0-553.171.1.rt7.512.el8_10, kernel-rt-modules-extra 4.18.0-553.171.1.rt7.512.el8_10, +2 more
    fixed: vendor fix RHSA-2026:75746
  • 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
    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
partial
Assessed
5d ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected products

  • Linux Linux

Classification

Weakness
Technology feeds

References

Sources

Fencer Intel 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.