FKIE_CVE-2026-63794
Vulnerability from fkie_nvd - Published: 2026-07-19 12:16 - Updated: 2026-07-19 12:16
Severity
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@]
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"arch/x86/kvm/svm/sev.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "f701ae476cb92a3a3d8844bb39bb63b4512684c8",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "64f2449841ffc7d203183aa4c748c9c77951ecc5",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "9349b50f4b11f135fe73b56cb2c2c872d8bc71d7",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "889c2a9c59897ca912bf39df5bb92555a0a13df4",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "e1a0fe288dee07b7da25a71e007c1ecd1080315b",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "720949ed666f34ff28ffdfe1471a5861d1e41fdf",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "2753a097d1fe24c4351c608048612c74108aa89f",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
},
{
"lessThan": "78ee2d50185a037b3d2452a97f3dad69c3f7f389",
"status": "affected",
"version": "24f41fb23a39bc2b6f190dcef35a5813a4bf183a",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"arch/x86/kvm/svm/sev.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "4.16"
},
{
"lessThan": "4.16",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.260",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.211",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.177",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.144",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.95",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.38",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.3",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: SVM: Fix page overflow in sev_dbg_crypt() for ENCRYPT path\n\nIn sev_dbg_crypt(), the per-iteration transfer length is bounded by\nthe source page offset (PAGE_SIZE - s_off) but not by the destination\npage offset (PAGE_SIZE - d_off). When d_off \u003e s_off, the encrypt\npath (__sev_dbg_encrypt_user) performs a read-modify-write using a\nsingle-page intermediate buffer (dst_tpage):\n\n 1. __sev_dbg_decrypt() expands the size to round_up(len + (d_off \u0026 15), 16)\n before issuing the PSP command. If len + (d_off \u0026 15) \u003e PAGE_SIZE,\n the PSP writes beyond the end of the 4096-byte dst_tpage allocation.\n\n 2. The subsequent memcpy()/copy_from_user() into\n page_address(dst_tpage) + (d_off \u0026 15) of \u0027len\u0027 bytes overflows\n by up to 15 bytes under the same condition.\n\nTrigger example: s_off = 0, d_off = 1, debug.len = PAGE_SIZE -\nthe PSP is instructed to write round_up(4097, 16) = 4112 bytes to\na 4096-byte buffer.\n\nFix by also bounding len by (PAGE_SIZE - d_off), the same check that\nsev_send_update_data() already performs for its single-page guest\nregion.\n\n ==================================================================\n BUG: KASAN: slab-use-after-free in sev_dbg_crypt+0x993/0xd10 [kvm_amd]\n Write of size 4095 at addr ff110062293bb009 by task sev_dbg_test/228214\n\n CPU: 96 UID: 0 PID: 228214 Comm: sev_dbg_test Tainted: G U W 7.0.0-smp--5ce9b0c48211-dbg #156 PREEMPTLAZY\n Tainted: [U]=USER, [W]=WARN\n Hardware name: Google Astoria/astoria, BIOS 0.20250817.1-0 08/25/2025\n Call Trace:\n \u003cTASK\u003e\n dump_stack_lvl+0x54/0x70\n print_report+0xbc/0x260\n kasan_report+0xa2/0xd0\n kasan_check_range+0x25f/0x2c0\n __asan_memcpy+0x40/0x70\n sev_dbg_crypt+0x993/0xd10 [kvm_amd]\n sev_mem_enc_ioctl+0x33c/0x450 [kvm_amd]\n kvm_vm_ioctl+0x65d/0x6d0 [kvm]\n __se_sys_ioctl+0xb2/0x100\n do_syscall_64+0xe8/0x870\n entry_SYSCALL_64_after_hwframe+0x4b/0x53\n \u003c/TASK\u003e\n\n The buggy address belongs to the physical page:\n page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x7fe72b6a0 pfn:0x62293bb\n memcg:ff11000112827d82\n flags: 0x1400000000000000(node=1|zone=1)\n raw: 1400000000000000 0000000000000000 dead000000000122 0000000000000000\n raw: 00000007fe72b6a0 0000000000000000 00000001ffffffff ff11000112827d82\n page dumped because: kasan: bad access detected\n\n Memory state around the buggy address:\n ff110062293bbf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n ff110062293bbf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00\n \u003eff110062293bc000: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc\n ^\n ff110062293bc080: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc\n ff110062293bc100: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc\n ==================================================================\n Disabling lock debugging due to kernel taint\n\n[sean: add sample KASAN splat, Fixes, and stable@]"
}
],
"id": "CVE-2026-63794",
"lastModified": "2026-07-19T12:16:51.757",
"metrics": {},
"published": "2026-07-19T12:16:51.757",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/2753a097d1fe24c4351c608048612c74108aa89f"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/64f2449841ffc7d203183aa4c748c9c77951ecc5"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/720949ed666f34ff28ffdfe1471a5861d1e41fdf"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/78ee2d50185a037b3d2452a97f3dad69c3f7f389"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/889c2a9c59897ca912bf39df5bb92555a0a13df4"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/9349b50f4b11f135fe73b56cb2c2c872d8bc71d7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/e1a0fe288dee07b7da25a71e007c1ecd1080315b"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/f701ae476cb92a3a3d8844bb39bb63b4512684c8"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
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