CVE-2026-63794: KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path

Q: What conditions are required to trigger the overflow?

An attacker needs local access and low privileges, as reflected by the CVSS vector. The vulnerable encrypt path is triggered when source and destination offsets differ such that the destination offset is greater than the source offset; the supplied example uses a source offset of 0, destination offset of 1, and a transfer length of one page.

Q: Which systems are identified as affected?

The affected software listed is the Linux kernel and Microsoft azl3 kernel version 6.6.143.1-1. The issue is in KVM's SVM SEV debug crypt encryption path.

Q: What is the impact of successful exploitation?

The encryption path can cause the PSP and subsequent memory-copy operations to write past a 4096-byte single-page intermediate buffer, by up to 15 bytes. The reported severity is high, with high confidentiality, integrity, and availability impact in the supplied CVSS vector.

Q: What does the fix change?

The fix additionally limits each transfer length by the remaining space in the destination page, PAGE_SIZE minus d_off. This prevents requests that would expand past the single-page destination buffer after the required 16-byte rounding.

Published Jul 19, 2026

Updated

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

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

In sevdbgcrypt(), the per-iteration transfer length is bounded by the source page offset (PAGESIZE - soff) but not by the destination page offset (PAGESIZE - doff). When doff > soff, the encrypt path (sevdbgencryptuser) performs a read-modify-write using a single-page intermediate buffer (dsttpage):

1. sevdbgdecrypt() expands the size to roundup(len + (doff & 15), 16) before issuing the PSP command. If len + (doff & 15) > PAGESIZE, the PSP writes beyond the end of the 4096-byte dsttpage allocation.

2. The subsequent memcpy()/copyfromuser() into pageaddress(dsttpage) + (doff & 15) of 'len' bytes overflows by up to 15 bytes under the same condition.

Trigger example: soff = 0, doff = 1, debug.len = PAGESIZE - the PSP is instructed to write roundup(4097, 16) = 4112 bytes to a 4096-byte buffer.

Fix by also bounding len by (PAGESIZE - doff), the same check that sevsendupdatedata() already performs for its single-page guest region.

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

CPU: 96 UID: 0 PID: 228214 Comm: sevdbgtest 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> dumpstacklvl+0x54/0x70 printreport+0xbc/0x260 kasanreport+0xa2/0xd0 kasancheckrange+0x25f/0x2c0 asanmemcpy+0x40/0x70 sevdbgcrypt+0x993/0xd10 [kvmamd] sevmemencioctl+0x33c/0x450 [kvmamd] kvmvmioctl+0x65d/0x6d0 [kvm] sesysioctl+0xb2/0x100 dosyscall64+0xe8/0x870 entrySYSCALL64afterhwframe+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@]

Affected Software

242 affected componentsFixes available

Linux Linux kernel=7.0.0-smp--5ce9b0c48211-dbg #156

Microsoft azl3 kernel 6.6.143.1-1<6.6.150.1-1

6.6.150.1-1

Linux Linux kernel>=4.16<5.10.260

Linux Linux kernel>=5.11<5.15.211

Linux Linux kernel>=5.16<6.1.177

Linux Linux kernel>=6.2<6.6.144

Linux Linux kernel>=6.7<6.12.95

Linux Linux kernel>=6.13<6.18.38

Linux Linux kernel>=6.19<7.1.3

linux/kernel>=4.16.0<5.10.260

5.10.260

linux/kernel>=5.11.0<5.15.211

5.15.211

linux/kernel>=5.16.0<6.1.177

6.1.177

linux/kernel>=6.2.0<6.6.144

6.6.144

linux/kernel>=6.7.0<6.12.95

6.12.95

linux/kernel>=6.13.0<6.18.38

6.18.38

linux/kernel>=6.19.0<7.1.3

7.1.3

ubuntu/linux-hwe-edge*

ubuntu/linux-aws-5.0*

ubuntu/linux-aws-5.3*

ubuntu/linux-aws-5.4*

ubuntu/linux-azure*

ubuntu/linux-azure-5.3*

ubuntu/linux-azure-5.4*

ubuntu/linux-azure-edge*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.3*

ubuntu/linux-gcp-5.4*

ubuntu/linux-gke-4.15*

ubuntu/linux-gke-5.4*

ubuntu/linux-gkeop-5.4*

ubuntu/linux-hwe*

ubuntu/linux-hwe-5.4*

ubuntu/linux-hwe-edge*

ubuntu/linux-ibm-5.4*

ubuntu/linux-oem*

ubuntu/linux-oracle-5.0*

ubuntu/linux-oracle-5.3*

ubuntu/linux-oracle-5.4*

ubuntu/linux-raspi-5.4*

ubuntu/linux*

ubuntu/linux-aws*

ubuntu/linux-aws-5.11*

ubuntu/linux-aws-5.13*

ubuntu/linux-aws-5.15<5.15.0-1117.124~20.04.1

5.15.0-1117.124~20.04.1

ubuntu/linux-aws-5.8*

ubuntu/linux-azure*

ubuntu/linux-azure-5.11*

ubuntu/linux-azure-5.13*

ubuntu/linux-azure-5.15<5.15.0-1123.132~20.04.1

5.15.0-1123.132~20.04.1

ubuntu/linux-azure-5.8*

ubuntu/linux-azure-fde*

ubuntu/linux-azure-fde-5.15<5.15.0-1122.131~20.04.1

5.15.0-1122.131~20.04.1

ubuntu/linux-bluefield*

ubuntu/linux-gcp*

ubuntu/linux-gcp-5.11*

ubuntu/linux-gcp-5.13*

ubuntu/linux-gcp-5.15<5.15.0-1118.128~20.04.1

5.15.0-1118.128~20.04.1

ubuntu/linux-gcp-5.8*

ubuntu/linux-gke*

ubuntu/linux-gke-5.15*

ubuntu/linux-gkeop*

ubuntu/linux-gkeop-5.15*

ubuntu/linux-hwe-5.11*

ubuntu/linux-hwe-5.13*

ubuntu/linux-hwe-5.15<5.15.0-198.208~20.04.1

5.15.0-198.208~20.04.1

ubuntu/linux-hwe-5.8*

ubuntu/linux-ibm*

ubuntu/linux-ibm-5.15<5.15.0-1111.115~20.04.1

5.15.0-1111.115~20.04.1

ubuntu/linux-intel-5.13*

ubuntu/linux-intel-iotg-5.15<5.15.0-1112.118~20.04.1

5.15.0-1112.118~20.04.1

ubuntu/linux-iot*

ubuntu/linux-kvm*

ubuntu/linux-lowlatency-hwe-5.15<5.15.0-195.205~20.04.1

5.15.0-195.205~20.04.1

ubuntu/linux-nvidia-tegra-5.15*

ubuntu/linux-oem-5.10*

ubuntu/linux-oem-5.13*

ubuntu/linux-oem-5.6*

ubuntu/linux-oracle*

ubuntu/linux-oracle-5.11*

ubuntu/linux-oracle-5.13*

ubuntu/linux-oracle-5.15<5.15.0-1114.120~20.04.1

5.15.0-1114.120~20.04.1

ubuntu/linux-oracle-5.8*

ubuntu/linux-raspi*

ubuntu/linux-raspi2*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.11*

ubuntu/linux-riscv-5.15<5.15.0-1111.115~20.04.1

5.15.0-1111.115~20.04.1

ubuntu/linux-riscv-5.8*

ubuntu/linux-xilinx-zynqmp*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux<5.15.0-198.208

5.15.0-198.208

ubuntu/linux-allwinner-5.19*

ubuntu/linux-aws<5.15.0-1117.124

5.15.0-1117.124

ubuntu/linux-aws-5.19*

ubuntu/linux-aws-6.2*

ubuntu/linux-aws-6.5*

ubuntu/linux-aws-6.8*

ubuntu/linux-azure<5.15.0-1123.132

5.15.0-1123.132

ubuntu/linux-azure-5.19*

ubuntu/linux-azure-6.2*

ubuntu/linux-azure-6.5*

ubuntu/linux-azure-6.8*

ubuntu/linux-azure-fde<5.15.0-1122.131

5.15.0-1122.131

ubuntu/linux-azure-fde-5.19*

ubuntu/linux-azure-fde-6.2*

ubuntu/linux-azure-fde-6.8*

ubuntu/linux-gcp<5.15.0-1118.128

5.15.0-1118.128

ubuntu/linux-gcp-5.19*

ubuntu/linux-gcp-6.2*

ubuntu/linux-gcp-6.5*

ubuntu/linux-gcp-6.8*

ubuntu/linux-gke<5.15.0-1113.119

5.15.0-1113.119

ubuntu/linux-gkeop<5.15.0-1100.108

5.15.0-1100.108

ubuntu/linux-hwe-5.19*

ubuntu/linux-hwe-6.2*

ubuntu/linux-hwe-6.5*

ubuntu/linux-ibm<5.15.0-1111.115

5.15.0-1111.115

ubuntu/linux-ibm-6.8*

ubuntu/linux-intel-iot-realtime*

ubuntu/linux-intel-iotg<5.15.0-1112.118

5.15.0-1112.118

ubuntu/linux-kvm<5.15.0-1109.114

5.15.0-1109.114

ubuntu/linux-lowlatency<5.15.0-195.205

5.15.0-195.205

ubuntu/linux-lowlatency-hwe-5.19*

ubuntu/linux-lowlatency-hwe-6.2*

ubuntu/linux-lowlatency-hwe-6.5*

ubuntu/linux-lowlatency-hwe-6.8*

ubuntu/linux-nvidia<5.15.0-1112.113

5.15.0-1112.113

ubuntu/linux-nvidia-6.2*

ubuntu/linux-nvidia-6.5*

ubuntu/linux-nvidia-6.8*

ubuntu/linux-nvidia-tegra*

ubuntu/linux-nvidia-tegra-igx*

ubuntu/linux-oem-5.17*

ubuntu/linux-oem-6.0*

ubuntu/linux-oem-6.1*

ubuntu/linux-oem-6.5*

ubuntu/linux-oracle<5.15.0-1114.120

5.15.0-1114.120

ubuntu/linux-oracle-6.5*

ubuntu/linux-oracle-6.8*

ubuntu/linux-raspi*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-5.19*

ubuntu/linux-riscv-6.5*

ubuntu/linux-riscv-6.8*

ubuntu/linux-starfive-5.19*

ubuntu/linux-starfive-6.2*

ubuntu/linux-starfive-6.5*

ubuntu/linux-xilinx-zynqmp<5.15.0-1080.84

5.15.0-1080.84

ubuntu/linux-bluefield<5.15.0-1101.103

5.15.0-1101.103

ubuntu/linux-intel-iot-realtime<5.15.0-1109.111

5.15.0-1109.111

ubuntu/linux-realtime<5.15.0-1116.125

5.15.0-1116.125

ubuntu/linux-realtime-6.8*

ubuntu/linux-aws-fips*

ubuntu/linux-azure-fips*

ubuntu/linux-fips*

ubuntu/linux-gcp-fips*

ubuntu/linux-aws-fips<5.15.0-1117.124+fips1

5.15.0-1117.124+fips1

ubuntu/linux-azure-fips<5.15.0-1123.132+fips1

5.15.0-1123.132+fips1

ubuntu/linux-fips<5.15.0-198.208+fips1

5.15.0-198.208+fips1

ubuntu/linux-gcp-fips<5.15.0-1118.128+fips1

5.15.0-1118.128+fips1

ubuntu/linux<6.8.0-147.147

6.8.0-147.147

ubuntu/linux-aws<6.8.0-1067.70

6.8.0-1067.70

ubuntu/linux-aws-6.14*

ubuntu/linux-aws-6.17*

ubuntu/linux-aws-7.0<7.0.0-1012.12~24.04.1

7.0.0-1012.12~24.04.1

ubuntu/linux-azure<6.8.0-1071.79

6.8.0-1071.79

ubuntu/linux-azure-6.11*

ubuntu/linux-azure-6.14*

ubuntu/linux-azure-6.17*

ubuntu/linux-azure-7.0<7.0.0-1014.14~24.04.1

7.0.0-1014.14~24.04.1

ubuntu/linux-azure-fde<6.8.0-1069.76

6.8.0-1069.76

ubuntu/linux-azure-fde-6.14*

ubuntu/linux-azure-fde-6.17*

ubuntu/linux-azure-fde-7.0<7.0.0-1013.13~24.04.1

7.0.0-1013.13~24.04.1

ubuntu/linux-azure-nvidia*

ubuntu/linux-azure-nvidia-6.14*

ubuntu/linux-gcp<6.8.0-1071.79

6.8.0-1071.79

ubuntu/linux-gcp-6.11*

ubuntu/linux-gcp-6.14*

ubuntu/linux-gcp-7.0<7.0.0-1011.11~24.04.1

7.0.0-1011.11~24.04.1

ubuntu/linux-gke<6.8.0-1066.74

6.8.0-1066.74

ubuntu/linux-gkeop<6.8.0-1052.56

6.8.0-1052.56

ubuntu/linux-hwe-6.11*

ubuntu/linux-hwe-6.14*

ubuntu/linux-hwe-6.17*

ubuntu/linux-hwe-7.0<7.0.0-31.31~24.04.1

7.0.0-31.31~24.04.1

ubuntu/linux-ibm<6.8.0-1067.68

6.8.0-1067.68

ubuntu/linux-lowlatency<6.8.0-147.147.1

6.8.0-147.147.1

ubuntu/linux-lowlatency-hwe-6.11*

ubuntu/linux-nvidia*

ubuntu/linux-nvidia-6.11*

ubuntu/linux-nvidia-6.17*

ubuntu/linux-nvidia-7.0<7.0.0-1018.18~24.04.1

7.0.0-1018.18~24.04.1

ubuntu/linux-nvidia-lowlatency*

ubuntu/linux-nvidia-tegra<6.8.0-1036.39

6.8.0-1036.39

ubuntu/linux-oem-6.11*

ubuntu/linux-oem-6.14*

ubuntu/linux-oem-6.17*

ubuntu/linux-oem-6.8*

ubuntu/linux-oracle<6.8.0-1064.67

6.8.0-1064.67

ubuntu/linux-oracle-6.14*

ubuntu/linux-oracle-6.17*

ubuntu/linux-oracle-7.0<7.0.0-1011.11~24.04.1

7.0.0-1011.11~24.04.1

ubuntu/linux-raspi*

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime*

ubuntu/linux-riscv*

ubuntu/linux-riscv-6.14*

ubuntu/linux-riscv-6.17*

ubuntu/linux-riscv-7.0<7.0.0-31.31.1~24.04.1

7.0.0-31.31.1~24.04.1

ubuntu/linux-xilinx*

ubuntu/linux-bluefield<6.8.0-1033.38

6.8.0-1033.38

ubuntu/linux-raspi-realtime*

ubuntu/linux-realtime<6.8.1-1062.63

6.8.1-1062.63

ubuntu/linux-realtime-6.14*

ubuntu/linux-realtime-6.17*

ubuntu/linux-aws-fips<6.8.0-1067.70+fips1

6.8.0-1067.70+fips1

ubuntu/linux-azure-fips<6.8.0-1071.79+fips1

6.8.0-1071.79+fips1

ubuntu/linux-fips<6.8.0-147.147+fips1

6.8.0-147.147+fips1

ubuntu/linux-gcp-fips<6.8.0-1071.79+fips1

6.8.0-1071.79+fips1

ubuntu/linux<7.0.0-31.31

7.0.0-31.31

ubuntu/linux-aws<7.0.0-1012.12

7.0.0-1012.12

ubuntu/linux-azure<7.0.0-1014.14

7.0.0-1014.14

ubuntu/linux-azure-fde<7.0.0-1013.13

7.0.0-1013.13

ubuntu/linux-gcp<7.0.0-1011.11

7.0.0-1011.11

ubuntu/linux-gke<7.0.0-1006.7

7.0.0-1006.7

ubuntu/linux-ibm<7.0.0-1013.13

7.0.0-1013.13

ubuntu/linux-nvidia<7.0.0-1018.18

7.0.0-1018.18

ubuntu/linux-nvidia-bos<7.0.0-2018.18

7.0.0-2018.18

ubuntu/linux-oem-7.0<7.0.0-1013.13

7.0.0-1013.13

ubuntu/linux-oracle<7.0.0-1011.11

7.0.0-1011.11

ubuntu/linux-raspi<7.0.0-1019.19

7.0.0-1019.19

ubuntu/linux-realtime<7.0.0-31.31.1

7.0.0-31.31.1

ubuntu/linux-riscv<7.0.0-31.31.1

7.0.0-31.31.1

Remediation

Recommended actions to resolve this vulnerability, in priority order.

Upgrade
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Fixed in 6.6.150.1-1
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Fixed in 5.10.260
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Fixed in 5.15.211
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Fixed in 6.1.177
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Fixed in 6.6.144
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Fixed in 6.12.95
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Fixed in 6.18.38
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Fixed in 7.1.3
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Fixed in 5.15.0-1117.124~20.04.1
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Fixed in 5.15.0-1123.132~20.04.1
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Fixed in 5.15.0-1122.131~20.04.1
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Fixed in 5.15.0-1118.128~20.04.1
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Fixed in 5.15.0-198.208~20.04.1
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Fixed in 5.15.0-1111.115~20.04.1
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Fixed in 5.15.0-1112.118~20.04.1
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Fixed in 5.15.0-195.205~20.04.1
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Fixed in 5.15.0-1114.120~20.04.1
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Fixed in 5.15.0-1111.115~20.04.1
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Fixed in 5.15.0-198.208
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Fixed in 5.15.0-1117.124
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Fixed in 5.15.0-1123.132
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Fixed in 5.15.0-1122.131
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Fixed in 5.15.0-1118.128
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Fixed in 5.15.0-1113.119
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Fixed in 5.15.0-1100.108
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Fixed in 5.15.0-1111.115
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Fixed in 5.15.0-1112.118
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Fixed in 5.15.0-1109.114
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Fixed in 5.15.0-195.205
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Fixed in 5.15.0-1112.113
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Fixed in 5.15.0-1114.120
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Fixed in 5.15.0-1080.84
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Fixed in 5.15.0-1101.103
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Fixed in 5.15.0-1109.111
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Fixed in 5.15.0-1116.125
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Fixed in 5.15.0-1117.124+fips1
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Fixed in 5.15.0-1123.132+fips1
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Fixed in 5.15.0-198.208+fips1
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Fixed in 5.15.0-1118.128+fips1
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Fixed in 6.8.0-147.147
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Fixed in 6.8.0-1067.70
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Fixed in 7.0.0-1012.12~24.04.1
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Fixed in 6.8.0-1071.79
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Fixed in 7.0.0-1014.14~24.04.1
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Fixed in 6.8.0-1069.76
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Fixed in 7.0.0-1013.13~24.04.1
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Fixed in 6.8.0-1071.79
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Fixed in 7.0.0-1011.11~24.04.1
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Fixed in 6.8.0-1066.74
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Fixed in 6.8.0-1052.56
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Fixed in 7.0.0-31.31~24.04.1
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Fixed in 6.8.0-1067.68
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Fixed in 6.8.0-147.147.1
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Fixed in 7.0.0-1018.18~24.04.1
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Compensating control
In KVM SVM's sev_dbg_crypt() ENCRYPT path, bound the per-iteration transfer length by both the source-page limit (PAGE_SIZE - s_off) and the destination-page limit (PAGE_SIZE - d_off), preventing PSP writes and subsequent copies from exceeding the 4096-byte dst_tpage allocation.

Event History

Jul 19, 2026

CVE Published

via MITRE·12:02 PM

Data Sourced

via MITRE·12:02 PM

Description

Data Sourced

via OSV·12:02 PM

DescriptionAffected Software

Data Sourced

via OSV·12:16 PM

Severity

Data Sourced

via NVD·12:16 PM

RemedyDescriptionSeverityWeaknessAffected Software

Jul 20, 2026

Data Sourced

via Microsoft·08:05 AM

DescriptionSeverityWeaknessAffected Software

Frequently Asked Questions

What conditions are required to trigger the overflow?

An attacker needs local access and low privileges, as reflected by the CVSS vector. The vulnerable encrypt path is triggered when source and destination offsets differ such that the destination offset is greater than the source offset; the supplied example uses a source offset of 0, destination offset of 1, and a transfer length of one page.

Which systems are identified as affected?

The affected software listed is the Linux kernel and Microsoft azl3 kernel version 6.6.143.1-1. The issue is in KVM's SVM SEV debug crypt encryption path.

What is the impact of successful exploitation?

The encryption path can cause the PSP and subsequent memory-copy operations to write past a 4096-byte single-page intermediate buffer, by up to 15 bytes. The reported severity is high, with high confidentiality, integrity, and availability impact in the supplied CVSS vector.

What does the fix change?

The fix additionally limits each transfer length by the remaining space in the destination page, PAGE_SIZE minus d_off. This prevents requests that would expand past the single-page destination buffer after the required 16-byte rounding.

CVE-2026-63794: KVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path

Affected Software

Remediation

Event History

Frequently Asked Questions

What conditions are required to trigger the overflow?

Which systems are identified as affected?

What is the impact of successful exploitation?

What does the fix change?

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